Lets see if it is a mod causing the issue.
Open your
includes/config.php and below<?php add this line:
PHP Code:
define('DISABLE_HOOKS', true);
So it looks like this:
PHP Code:
<?php
define('DISABLE_HOOKS', true);
/*======================================================================*\
|| #################################################################### ||
|| # vBulletin 4.2.2
If the error goes away, then remove the
define('DISABLE_HOOKS', true); from the config.php and then start disabling each mod one a a time till you find the culprit.