Ok lets do this, disable plugins via the includes/config.php file.
To do that open your includes/config.php file and below <?php add the following.
PHP Code:
define('DISABLE_HOOKS', true);
So it looks like this:
PHP Code:
<?php
define('DISABLE_HOOKS', true);
/*================================================= =====================*\
|| ################################################## ################## ||
|| # vBulletin 4.2.2
Use a editor like notepad++ to edit any files, don't use Notepad or Wordpad.
If that fixes the issue enable plugins again by adding // before the line you added, then navigate to ACP --> Plugins & Products --> Manage Products and disable one mod at a time until you find the one causing the issue.