I did have a problem where I srewed up the usergroup database. I reinstalled that table and checked all the permissions but Registered users don't have the ability to bid on ads. Could this be affected by another table somewhere?
I don't exactly remember what I did to initially screw up the table but I know it has been talked about before. It was probably during my second or third install
and the outcome was that I showed two administrators and two banned users and some missing. So I just dropped that table and replaced it with a good one.