sounds like a hack job - we had something similar happen at ubbdev, but that was using a version previous to 6.3 and a script kiddie was automatically registering hundreds of people per minute, it corrupted the memberslist.cgi file and started writing over the older member files. Infopop fixed it soon after and I re-wrote 20-30 member files by hand :/
Anyways, be sure you have some sort of flood protection turned on, even if it's just 10 seconds - that'll foil most kiddie hackers so that at least it doesn't happen to you <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />
