Sorry to resurrect an old thread, but I was searching for an answer to this same problem about registering users and came across this.
I had already rebuilt member stats once, but I did it again after reading this thread and still have no luck. It won't let anyone register.
This actually started with some problems I was having with a guy who registered but never got his password emailed to him, in spite of entering the correct email address and receiving all other emails being sent to him. We tried all kinds of things to get his password to him; then I looked it up manually and sent it to him. At that point, I was able to log on as him, but he was not able to log in as himself -- and yeah, we checked case sensitivity, etc.
So this morning I rebuilt member stats and everything I could think of that might be a problem, and then I told him to try a couple more things and if all else fails to re-register under a different name to see if that worked. And that's when this problem started. It seems odd that the two things might be related, but this guy is the ONLY one who's had problems using the BB in the past week, and it just is so oddly coincidental that this registration problem cropped up when he tried to register again.
Can anyone help? I'm totally at a loss and really, really frustrated. Thanks!
P.S. We are using UBB classic, version 188.8.131.52, and the board URL is http://www.softrak.com/cgi-bin/ultimatebb.cgi