It is the heat, and its not a bad card . A game runs 50-60 fps then drops to 5-10 fps then goes back again. (hence you know your drivers work, they dont go bad then good again for the most part) I had to send my pc back to HP because the GPU fryed and I was runing at a constant 3fps. The problems started happening again with a new motherboard (and the onboard gpu). I downloaded speedfan to see my GPU temp and it was running at ~110C. (should be no greater than 80ish at full load). You are essentialy slowly cooking your graphics card!
There are no cooling fans anywhere near the the NVIDIA 9100 GPU on an ASUS (Pegatron) Motherboard. There is a small heat sink but thats it. When you turn your comp on it heats up to 70C in 5 minutes. Takes WOW another 5 minutes to get it past 120C where it partialy shuts itself off to (hopefully) avoid damage hence 5 frames per second (if you use any other app that uses 3D rendering different than wow they wont work either for that duration). The GPU then cools down and you get to 50-60fps for a bit untill it overheats again.
The temporary solution is ventilation, clean your box, wipe your fans get your box off the carpet away from other heat sources. When raiding or if the effects are intensive open the side your case up.
Permanent solution: buy a $5 fan that ventilates over the gpu.