I was a way a few days so I wanted to update this thread. It turns out that my modified VRM cooler was not making very good contact with the VRM on the graphics card itself. I still need a more permanent fix, but for now.... wedged a small wooden shim so that it presses tighter against the VRM and the problem is solved. I'm going to mount it better when I pull the card in a few days to upgrade my PSU and add a second 6950 for crossfire.
So..heat is the culprit..even with an Arctic cooler 7950 3 fan system running.
I had flashed the card back to to a 6950 when troubleshooting the problem...but put it back to the 6970 specs again once I figured out what the problem was. For now I'm running it at 880/1375 till I fix the VRM's cooler better.