Viewing Rails model page works on first view but not subsequent views

Question

This is using Rails 2.2.2

I have a model that uses the acts_as_flaggable plugin, and on the page I use to display an instance of the model, I list any flags that the model has.

When I start my Rails dev server(mongrel) using the standard script/server command, load the page holding the following code, it loads fine:

<% @object.flags.each do |flag| %>
<tr>
<td><%= time_ago_in_words(flag.created_at) %> ago</td>
<td><%= flag.flag %></td>
<td><%= link_to flag.user.login, user_path(flag.user) %></td>
</tr>
<% end %>

If I reload the page(and on any subsequent views), I get the following NoMethodError error:

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.include?

If I restart the dev server, the page loads fine again one time then subsequent views yield the same strangeness.

If I remove the line:

<td><%= link_to flag.user.login, user_path(flag.user) %></td>

The page loads fine and will reload fine from then on.

It seems as if the flaggable plugin is having trouble with the user model for some reason, but then why does it work on the first page load? I also can't seem to repeat the problem using script/console.

--EDIT--

Adding in the stack trace per request. Under normal circumstances I usually can handle this particular error, but the part that is confusing me is why it works the first time.

Here is the error page/trace as it appears to me, I hope this proves to be helpful:

NoMethodError in Admin#list_flagged

Showing app/views/admin/list_flagged.html.erb where line #65 raised:

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.include?

Extracted source (around line #65):

62:                   <tr>
63:                     <td><%= time_ago_in_words(flag.created_at) %> ago</td>
64:                     <td><%= flag.flag %></td>
65:                     <td><%= link_to flag.user.login, user_path(flag.user) %></td>
66:                   </tr>
67:                 <% end %>

RAILS_ROOT: /dev/trunk
Application Trace | Framework Trace | Full Trace

/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:142:in `create_time_zone_conversion_attribute?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:75:in `define_attribute_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:71:in `each'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:71:in `define_attribute_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:350:in `respond_to?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:209:in `method_missing'
app/views/admin/list_flagged.html.erb:65
app/views/admin/list_flagged.html.erb:61
app/views/admin/list_flagged.html.erb:24:in `each'
app/views/admin/list_flagged.html.erb:24
app/views/admin/list_flagged.html.erb:14

/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:142:in `create_time_zone_conversion_attribute?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:75:in `define_attribute_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:71:in `each'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:71:in `define_attribute_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:350:in `respond_to?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:209:in `method_missing'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_collection.rb:359:in `method_missing_without_paginate'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `method_missing'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `each'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `send'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `method_missing'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_collection.rb:359:in `method_missing_without_paginate'
/usr/lib/ruby/gems/1.8/gems/mislav-will_paginate-2.3.6/lib/will_paginate/finder.rb:167:in `method_missing'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/form_helper.rb:313:in `fields_for'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/form_helper.rb:253:in `form_for'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:39:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:39:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/template.rb:73:in `render_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:256:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:367:in `_render_with_layout'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:254:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:1174:in `render_for_file'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:896:in `render_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/core_ext/benchmark.rb:8:in `realtime'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:868:in `render_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/core_ext/benchmark.rb:8:in `realtime'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:1248:in `default_render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:1254:in `perform_action_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:617:in `call_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:610:in `perform_action_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/1.8/benchmark.rb:293:in `measure'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/rescue.rb:136:in `perform_action_without_caching'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/caching/sql_cache.rb:13:in `perform_action'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/query_cache.rb:8:in `cache'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/caching/sql_cache.rb:12:in `perform_action'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:524:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:524:in `process_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:606:in `process_without_session_management_support'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/session_management.rb:134:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:392:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:183:in `handle_request'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:110:in `dispatch_unlocked'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:123:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:122:in `synchronize'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:122:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:132:in `dispatch_cgi'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:39:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:76:in `process'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:74:in `synchronize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:74:in `process'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:159:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `each'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:282:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:281:in `each'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:281:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:128:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/command.rb:212:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:281
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:142:in `load_without_new_constant_marking'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:142:in `load'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:521:in `new_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:142:in `load'
/usr/lib/ruby/gems/1.8/gems/rails-2.2.2/lib/commands/servers/mongrel.rb:64
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:153:in `require'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:521:in `new_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:153:in `require'
/usr/lib/ruby/gems/1.8/gems/rails-2.2.2/lib/commands/server.rb:49
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
script/server:3

/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:142:in `create_time_zone_conversion_attribute?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:75:in `define_attribute_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:71:in `each'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:71:in `define_attribute_methods'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/attribute_methods.rb:350:in `respond_to?'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:209:in `method_missing'
app/views/admin/list_flagged.html.erb:65
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_collection.rb:359:in `method_missing_without_paginate'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `method_missing'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `each'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `send'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_proxy.rb:212:in `method_missing'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/associations/association_collection.rb:359:in `method_missing_without_paginate'
/usr/lib/ruby/gems/1.8/gems/mislav-will_paginate-2.3.6/lib/will_paginate/finder.rb:167:in `method_missing'
app/views/admin/list_flagged.html.erb:61
app/views/admin/list_flagged.html.erb:24:in `each'
app/views/admin/list_flagged.html.erb:24
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/form_helper.rb:313:in `fields_for'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/helpers/form_helper.rb:253:in `form_for'
app/views/admin/list_flagged.html.erb:14
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:39:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:39:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/template.rb:73:in `render_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:256:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:367:in `_render_with_layout'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/base.rb:254:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:1174:in `render_for_file'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:896:in `render_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/core_ext/benchmark.rb:8:in `realtime'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:868:in `render_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/core_ext/benchmark.rb:8:in `realtime'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:1248:in `default_render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:1254:in `perform_action_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:617:in `call_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:610:in `perform_action_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/1.8/benchmark.rb:293:in `measure'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/rescue.rb:136:in `perform_action_without_caching'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/caching/sql_cache.rb:13:in `perform_action'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.2.2/lib/active_record/query_cache.rb:8:in `cache'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/caching/sql_cache.rb:12:in `perform_action'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:524:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:524:in `process_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:606:in `process_without_session_management_support'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/session_management.rb:134:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:392:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:183:in `handle_request'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:110:in `dispatch_unlocked'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:123:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:122:in `synchronize'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:122:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:132:in `dispatch_cgi'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_controller/dispatcher.rb:39:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:76:in `process'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:74:in `synchronize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/rails.rb:74:in `process'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:159:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `each'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:282:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:281:in `each'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/configurator.rb:281:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:128:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel/command.rb:212:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/bin/mongrel_rails:281
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:142:in `load_without_new_constant_marking'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:142:in `load'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:521:in `new_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:142:in `load'
/usr/lib/ruby/gems/1.8/gems/rails-2.2.2/lib/commands/servers/mongrel.rb:64
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:153:in `require'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:521:in `new_constants_in'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:153:in `require'
/usr/lib/ruby/gems/1.8/gems/rails-2.2.2/lib/commands/server.rb:49
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
script/server:3

Request

Parameters:

None

Show session dump

--- 
:user_id: 1
:last_page: http://localhost:3000/
flash: !map:ActionController::Flash::FlashHash {}

Response

Headers:

{"cookie"=>[],
 "Content-Type"=>"text/html",
 "Cache-Control"=>"no-cache"}

--EDIT #2--

Well, I've "fixed" it. Despite the fact that there is a belongs_to relation in the Flag model, I added the following code to the Flag model from acts_as_flaggable:

def user
  User.find(self.user_id)
end

This code does allow the page to load without error whether it is the first time on the page or the Nth.

I would have added this as an answer, but I don't know that I am satisfied with this.

Answer 1

Having experience a similar problem, I'd check your /config/initializers directory. Does it declare some methods or include some modules into the models? If so, it will happen on first load, but the models will get reloaded on subsequent requests without the initializers running again.

Answer 2

No true fix, but here's a workaround. It has to do with the config.cache_classes setting in the development.rb file.

Change:

config.cache_classes = false

to...

config.cache_classes = true

and the problem goes away.

Not a great solution, but it seems to have been around since 2.2.2 (I'm on 2.3.12).

Lots of background and a possible patch here.

This was my first clue.