Fatal error: Call to undefined function is_multisite()?

Question

Recently i updated wordpress 3.0 automatically. Before update, everything working fine. After the update, page is displayed with error message

Fatal error: Call to undefined function is_multisite() in /home1/servername/public_html/myfolder/mysite/wp-includes/wp-db.php on line 505

I then overwritten all the files with new version files from FTP. But still I am having the same problem. Can anyone help me to solve this problem. Thanks in advance.

Answer 1

FTP the file wp-includes/load.php and wp-settings.php and check that;

1. wp-includes/load.php line 578 is function is_multisite()
2. wp-settings.php line line 19 is require( ABSPATH . WPINC . '/load.php' );

If that's all ok, disable any troublemaking plugins by deleting them or temporarily renaming them in your plugins folder.