There seems to be a problem with NickBan, at least with version 6.04. In the check_name_bans function, you have this:
The problem is that if someone enters an invalid nick during registration, no HTTP header is written out, so the user is given a download dialog. It looks like you need to modify it to this:
Once I made this change, it worked as expected, displaying an error to the user that their nick was invalid and to go back and try again.
