Have not reproduced it via various load tests and Dirt 3 gaming. But both times it seemed to happen when computer was sleeping and then woken up. I did test setting sleep to 1 minute to force sleep, and did not reproduce it that way either.
I also had to reduce what I thought was a previously stable OC to prevent issues, but I am not sure if that's a driver difference, or a card issue...trying to reduce variables, by first getting back to a stable overclock (so far, 860/1350 on the 6950s seems stable with max voltage allowed by Trixx.)
So nothing definitive to report.
On the bright side, Dirt 3 finally runs with decent frame rates ( > 100) except in the rain
Rain definitely seems to bring fps down by a lot.