I don't think my crashing has to do with my video card but I do have random lag spikes with my crossfire mobility radeon hd 5870. I'm at 60 fps...next minute I'm at 15 for no reason. Nothing in the environment is causing me to lag. Like I'll be by myself or in a cut scene when it happens. I seem to crash when I alt-tab too much. I don't really have random lag spikes with my crossfire off but I get better fps with it on with max settings.