It may be from a mod, try disabling them all and see if the issue still persists.
Open your
includes/config.php file 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