Hmm, I don't have any experience with this card but there's a couple of things. First off, make sure you have the latest Drivers direct from the NVidia site, drivers that come with the card are bound to be outdated and older drivers won't work with GPU3. If you have no joy with that then delete the GPU3 client and go back to GPU2 which is more stable.
Might be a good idea to check with Stanford to see what video cards are approved for the GPU folding regimen.
Card is supported, quite a few using this...gives around 10k per day