CG is the best! It runs fine on my 6950.
Which driver, SDK, miner versions do you run?
What symptoms are you experiencing?
I have a 6990 and 2x 6970's in one pc but the 6970's each run 30 hash's behind the others. I'm using the 11.11 drivers. Same thing I use on my other computers, not sure whats causing it. They all run at the same speed with guiminer but it's not that fast.