spammers unbanning themselves!

Hi, i have a daily delema, the spammers i ban and deactivate, are being unbanned, i have altered password for admin yet it happens daily..... any ideas? i use Paid Join to stop most of them, however, i still get some, now with them unbanning themselves what do i do?

Did you see this?

http://www.boonex.com/forums/?action=goto&my_threads=1#topic/Why-Baning-members-doesn-t-hold-more-than-24-hours-.htm

cheers newton, i will try those suggestions.