[ForceHSS]

Did you install anything else apart from this plugin before this problem. Also, when you updated to 4.2.2 did you put the fix into your config as this can cause problems if not done the best thing you can do is disable all plugins via config use notepad++ to edit the config

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 an editor like notepad++ to edit any files, don't use Notepad or Wordpad.
After you have done this update to 4.2.3 as the fixes are in this version it would be good if you could login to the admincp to turn the board off first, but if you can make a post to tell your members what is going to happen