Well, all I have to say is get rid of the stupid Itemshop. The one you have is the one I modified from a friends and it totally sucks. Most people wouldn't believe me, but the main one circulating right now is one that I pretty much wrote. I added the sell feature, the mutliple items(original was only 1 item per user), and also wrote a very good and working "money-per-post" addition.
Otherwise, the forums are great.
EDIT: also, there is a big error in that Itemshop. Check out the "AX-Credits" of the test user now

A bug in the sell feature that I found after I wrote it. Back then I could never fix it.