I have built a new system. It includes an Asus P5Q Deluxe MB, Intel Q9550 CPU, Kingston HyperX RAM (8 GBs), 850 Watt Antec PS and an ATI 4870 video card. I installed Vista 64 Ultimate on this machine and the load went smoothly. I updated all drivers from Asus support and ATI. The machine works properly under normal use but blacks out the screen and locks the system when using graphics-intensive apps. If I run 3DMark this occurs as well as when something like WOW is run. I can run the programs without issue when using my old ATI X700 card but as soon as I try one of those programs with the new video card it locks up solid and I have to shut it down manually. I have checked the event viewer but there is nothing there. Any ideas?
Also, did your card come with temp monitoring utilities? Make sure your temps are ok.
TK