After prolonged play I start getting all kinds of graphical artifacts - large swathes of grey boxes and distortion and unable to see. If I hit esc and go to the menu and sit for a second it goes away, but then quickly recurs. Doesn't happen at all unless I play for a long period of time. I saw the same problem in the past with a passively cooled vid card on an old PC I had - I think it's the chipset/graphics card overheating. I have the X1900 in a mac pro 3ghz machine. I don't really hear the fan ramping up too much on the machine however. Is there a way to manually crank up the fan when playing, or at least to check whether it's speeding up as it should? I am running 1600x1200 with 3x AA and other options fairly high. The system runs fine with good frame rate, until it overheats.