With web applications especially, it's very hard to diagnose a problem without seeing the code. You're maintaining a lot of state through a combination of client cookie, database table, and script logic, and on top of that, the setup makes it hard to debug. The problem could be anywhere.

Reading about it in prose makes it even harder - remember that the code may not be doing what you think it's doing! Putting up the Perl helps us get to the meat of the problem - just don't neglect the READMORE tag.

Good luck!