something like this has happend to me before. someone got into my account and started attacking another person on the board, I knew nothing of it, I just started getting PMs from people calling me a lier and a "spoiled brat in dire need of pshcological help" and of coarse people did not beleive me, and I got banned from that board and another one that was linked to it... they eventually found the real culprit and I am back on those boards(greytalk was one of em) but I had to change my password and username everywhere on the net.