So I just bought a Radeon 6850 which was happily churning out a good ~200 Mh/s.  After a day or so of running, it's now running at a top speed of ~70 Mh/s.  I've had the fan manually on fully speed and it's definitely not overheated.  I've quit all programs as well, and the catalyst center shows 100% activity.   Any idea why this happened?  Did I blow one of the gpus?

edit: with a second restart, I'm now getting ~200 again, but it fluctuates a whole lot.  strange