I replaced my GeForce 7800 GS with a Sapphire X1950 PRO 512 AGP card and now the screen goes black at all resolutions/refreash rates after several minutes using the latest ATI drivers, but works fine with the basic Win drivers. Occasionally, moving the mouse will bring it back if I catch it in time, but only once. Sreen saver/hibernation/sleep all turned off. It acts like it's a heating issue. Also did this with a Diamond X1950 Pro...
Any thoughts would be appreciated.
This is probably the same problem a lot of ppl are having with the x1950Pro (search Sapphire x1950Pro forums). I don't think it's a design flaw but a failure in one of the components. ATi designed the x1950Pro with digital VRM (voltage regulators) and did away with the capacitors nVidia still uses them even in the GF8800GTX. These digital VRM's are overheating or faulty causing improper voltage going to the GPU, Mem or both. This results in crashing the vid card and the whole system which you see as the "Black Screen/Standby Mode"
I am having the same problem with my PCI-E x1950Pro from Asus. With all the great reviews on this card and they never reported a problem I think a bad batch of cards is what we got. The only thing you can do is RMA and hope your replacement is in full working order.