Thanks for the link sent in PM. I've looked at the code and it seems there is a problem with your GAL configuration.
The error comes from the $username variable used in quotes bbcode ! It is replaced by
Code:
<a rel='nofollow' href='http://www.cornishserver.com/forums/private.php?do=newpm&u=21' target='_blank' class='gal' onmouseover='GAL_popup(this,"1", 0, "style=\"border: 1pt solid #000000;\"", "Private Message Private Parts", "style=\"background: #FFFFCC;padding: 2px;font-size: 10px;\"");' onmouseout='GAL_hidepopup();'>Private Parts</a>
</div>
Check your configuration... the problem doesn't come from this hack. Just a question : don't you have a problem with the normal vB bbcodes ? I'm sure TheGeek will have a solution