If anyone has any new info on this subject I'd be interested to hear it. It looks like the same thing happened to us.
Last night while two sysops and several players were on our server, someone came in, asked who the admins were, and 10 seconds later we were both "permenantly banned from the server by PB; banned by admin!" I shut down the server immediately to see what had happened and limit any additional data corruption. (As the server was shutting down, another person with the same tags [s-S] was trying to enter... it looked like an invasion!)
I traced the IP of the guy who did it and he shows up as "clean" in the MPI. There's no normal way I know of that anyone could do that. I found our names listed on the local pbban.dat file, and our admin.cfg and clan.cfg files were corrupted (no readable new entries, but damaged data). There were no other suspicious entries in any of the log files, other than them showing we had been kicked.
Any suggestions? Is there some new server hack circulating?