I was trying the banning system in my local machine..
so I registered a new member then banned him by "user" not ISP nor IP!
everything went ok and the reason of banning message appeared .. so I logged out and tried to loging with the adminstrative account .. but the banning message was there with the same name of the banned member !!
I set the banning to be for one day only but up to now (more than week) I can't login anymore ! :(
in my case it's easy to fix the situation by accessing phpMyAdmin and deleting the record but if this happened in a public computer (internet caffee) people will suffer !