I'm running GUIminer on my desktop computer, using an ATI Radion 5670. I normally average about 75-85 Mhash/s while I'm using the computer, a tad more when I'm not.
This is the second time that GUIminer has seemed to 'glitch', my GPU is running now at 4Mhash/s. No apparent reason that I can see, doesn't seem to be overheating or anything like that, but here's a screenshot of my GPU stats - http://i.imgur.com/RKD13.png
This is happened to me on two different pools, once on Ars and once on NoFeeMining...I don't think it's an issue of not having work. A restart does seem to fix the problem, but I figured I'd post here in case someone had an idea of how I could stop this from happening.