Well...I have never used a radeon card, so take this advice how you will. I would advise to at least attempt to install an older set of drivers for the card (or newer if ATI has them released) to see if that makes a difference. I know that if I have an issue with any of Nvidia's drivers, I have always compared results with a few other sets. My op. Good luck man, there is nothing more frustrating then to be in the heat of battle and have your pc lock up or shutdown on you!!! :P
hifi