Lately i up-to-date wordpress 3. instantly. Before update, everything working fine. Following the update, page is displayed with error message

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

Then i overwritten all of the files with latest version files from FTP. But nonetheless I'm getting exactly the same problem. Can anybody assist me to to resolve this issue. Thanks ahead of time.

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

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

If that is all ok, disable any troublemaking plug ins by removing them or temporarily renaming them inside your plug ins folder.

Or if you work with SVN, remove the wordpress-includes folder and also the wordpress-configurations.php file and do and 'svn up'