if you just want to clean out all bans in one click (query)..
just truncate the ubbt_BANNED_USERS table...
there are two other tables you might also do the same to, namely:
ubbt_BANNED_EMAILS
ubbt_BANNED_HOSTS
sql syntax is:
truncate TABLE ubbt_BANNED_XXXXX
where the XXXXX is USERS, EMAILS, and/or HOSTS
then you can start fresh and save your fingers from being sore from clicking on each individually

you can run those queries from phpMyAdmin or from your ubbthreads Admin Control Panel - Database Tools - SQL command
