^ he speaks the truth, sort of (I have the 250 folding flawlessly with the 8800gts') has to do with the processing cores i think. They need to be the same from what I remember, I had major ppd drops when I folded the 260 with the 9800gt or the 8800gts or the 9800gtx. But the 8800gts and the 9800gtx as well as the 250 all fold together no issues (same # of core processors).