Thanks for the replies. I think the card is getting plenty of power, although I may check that as a last resort.

I've played with the thread concurrency a bit:
8000 didn't make any difference.
4096 I get HW Errors.
Any higher than 8192 and I get black screen and the card crashes.

I did the setx stuff.

I'm trying yet another pool now to see if that will make any difference. Will report back.

Update: The other pool seems to be having server issues(wemineltc), so not good for testing right now. I'm still at a loss.