GTX470 Artifacts/Crashes and sometimes stretched geometry

Hi.

I'm having "ANOTHER" Problem with my GTX470, This time it's graphical corruption, display crashes and glitches..



The games iv'e noticed these in are: Supersonic Sled, GTA 4, Blur and L4D.
My problem is, after a while of playing, rarely and i do mean rarely, the game will freeze and pieces of the screen will be mixed around in a checkerboard pattern, and only 1 time out of the 3-4 crashes, has the computer recovered from the error without cutting the power.  

While playing supersonic sled once, the sled became a massively elongated thin piece of stretched geometry until i restarted it, which made me immediately think of overheating.  


BUT in every instance, the temperatures reached a maximum of 96C until the fans bolted down at only 70%.
Is this a sign of bad VRAM? i hope not since i really want to SLI this card, and iv'e already ordered the second and
IF it is bad VRAM, will simply underclocking it allow it to regain stability? or is the damage permanent and physical..  

Plus the card has never been overclocked.  


Specs:
AMD Phenom II X4 955BE 3.2GHz
GTX470 + GTX285 (Physx)
4GB DDR3 1333MHz RAM
Antec 1200 Case (no cooling problems i think)
Antec TPQ 1000W PSU