Magento 1.7 Admin Login Fatal error: Call to a member function getBlockName() on a non-object in line 43

Question

Can someone help me?

On index.php/admin the following exception was thrown:

Fatal error: Call to a member function getBlockName() on a non-object in /home/ahorraen/public_html/app/code/core/Mage/Captcha/Block/Captcha.php on line 43

Answer 1

Delete var/cache and var/session

This works for me!

Answer 2

Clearing the cache works for me.

Just remove var/cache/All folders

Even after removing it may take few minutes to get refreshed.

Answer 3

Only cache/ and session/ don't work for me. Set properly chmod write permissions of folders

var
var/cache
var/session

Answer 4

There are a few things that would cause this, such as incorrectly overwriting the admin/captcha/type field in a community or local module. However, this is most likely to be an issue with the cache as others suggested. Make sure that you clear all caches that you have, including Memcached, Redis and/or APC.

See my answer over here for more details: https://stackoverflow.com/a/25902858/1038564