This post consolidates two known problems and their solutions/workrounds. I'll ask the mods to add any other similar issues to the thread as we discover them.
1) Sleeping Monitor Bug
Drivers affected: 295.51 (BETA), 295.73 and 296.10
Hardware affected: Any nVidia card connected to a DVI or HDMI monitor.
Symptom: If Windows power management blanks the screen, putting the monitor to sleep, the Cuda device becomes unavailable and SETI Cuda tasks run extremely slowly and/or error out.
Either (a) set Windows power management never to blank the screen
or (b) Install a different graphics driver, downloadable from http://www.nvidia.com/Download/Find.aspx?lang=en-us
2) Kepler cards unsupported
Drivers affected: All drivers from 304.48 (BETA) onwards.
Hardware affected: nVidia 'Kepler' - GT 6xx and GTX 6xx cards.
Symptom: All tasks end in errors when using the stock v6.10 'cuda_fermi' application.
a) Use an optimised Cuda application, where available.
b) Downgrade to the 301.42 driver - only possible on GTX 670/680/690 cards, not on newer releases like the 650/660 or their Ti variants.
c) Set an environment variable, as shown below.
The environment variable to use is
and it needs to have the value 1 (one)
You need to be running in Administrator mode, and you need to be running at least driver 306.02 (BETA) or 306.23 (WHQL)
Here's how to reach the setting screen: