[ozzy47]

Yes the full error from your server error logs would help.
What version of vB4 are you running?
What PHP version are you running?

But we can see if this is from a mod, by doing the following.

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

Then try and register and see what happens.