One thought. I know vbulletin does not guarantee access to the support forums as part of the license. You can be banned for bad behavior from vbulletin.com and not receive a refund.
If this site has a similar policy, you may be out your money.
BUT, banning from vbulletin.com does not preclude you from downloading the code. If you can not download the code you paid for, you may have a legitimate gripe. Perhaps the Better Business Bureau in the area where the script seller is running his business - but that wouldn't help much.
My best advice is to use these guys:
http://www.consumerhelpweb.com/ They helped me when a national news site plagiarized one of my quizzes. I am not sure about their current pricing, but it wan't high when I used them.