[Lynne]

Try creating a default style and see if you still have the problem - Styles & Templates > Style Manager > Add New Style > no parent - then browse the site using that totally default vbulletin style - do you still have the same problem? And, make sure your plugins are still of when you browse the site using the default style -
Note: To temporarily disable the plugin system, edit config.php and add this line right under <?php

PHP Code:

define('DISABLE_HOOKS', true);