Heroin

I recently found out that a relatively new player, Heroin, was banned for cheating last summer. Can you tell me how this cheating was detected? I've played against him several times, and every time I press F2, his game crashes. I thought he was using some kind of cheat, but then, when we started playing again, I pressed F2 immediately, and his game crashed again. Maybe it's just a bug in the HD mod?