URGENT
Found a very large problem. When a ticket is submitted, they are given a URL. If they change the number of the ticket in that URL to a different number, you can view other users tickets. That completely nulls the usage of the Usergroup Settings.
http://forums.website.com/helpdesk.php?do=ticket&tid=6
If you change the number 6 to the number 7, you can view the next ticket AND you can reply to it.
You really need to fix this.