ubbt_USER_PROFILE, ubbt_USERS, ubbt_USER_DATA
are the tables and there is a record for each member in each table. usually, ubbt_USER_PROFILE is the culprit, but this is only based upon the statistics i gleaned empirically fixing this issue..
phpMyAdmin is a way to edit them, usually from your hosting control panel, there is a link.
if you are confused at this point, i'd recommend hiring a pro.
edit: and after re-reading the problems you are having, i'd suspect maybe your server / hosting environment might be a bit too touchy on security as well... maybe mod_security?
not sure... but if you can actually pull up a user profile and see it, then it's not misaligned user tables..
sorry for my not reading carefully
regardless: it might take a pro to really flesh out the problem
