Ah, OK. So there must still be a driver conflict or something of that nature on Puma w/ the ATI cards. Cheetah, with the 2 CUDA cards is pulling WUs fine now, after I updated the nVidia driver like Al suggested. Guess it's time to put on the nerd hat and see what's up with the ATI rig... Something is definitely weird though, because it appeared to uninstall 12.3 Catalyst drivers just fine...rebooted, and then installed 12.4...rebooted again, and then checked it - still says 12.3 Catalyst for some strange reason.