I have a 6970 that was overheating (92 C) even when it was not over-clocked.
I took off the heat sink and this is what I found?!
Notice how two of the heat pipes dont even touch the GPU! Also the surface is far from flat.
Once again Asus have failed on the thermal paste, it was dry and not spread correctly.
I cleaned it off put some MX3 and now even when over-clocked to 940 MHz my GPU temp is 72C ! Even with the case closed.
Same thing happened to my Asus motherboard, chipset was overheating. Took off heat sink and there was a couple of little dots of thermal paste.