4GB Corsair Dominator
2 x Diamond HD3870 512MB with Catalyst 9.11
Windows XP x64
While I'm using windows, at random times (still haven't figured out a pattern to the crash), the screen freezes, the mouse still works but anything I click on will not respond, eventually the screen goes off and after 5-10 secs it usually comes back on with an ATI message stating that the video driver has just recovered with the option to send a report. Half the times after the screen goes off the driver will not recover having to restart my machine.
One or both of the cards could be over heating but since you did mention any thing about overlcoking I assume that you are not at this time. First check the cards for any major dust build up and test them separately to rull out a dud. Make sure that your psu is good enough or not failing.