I've only played once since, but DX9 appears to have fixed a lockup problem I had (well, DX9, or having the lastest drivers for my Radeon 8500, or both). When I would exit a game, whether part of the way through, or at the end, the machine would freeze. Most of the time, after random button mashing and keyboarding, it would come back to the main screen (as it should) but sometimes it wouldn't, forcing a hard reboot. The problem appears gone now, woohoo!