Summary of my 8.41 runs:

The 50 or so workunits on my x64 Windows Vista computer with a GeForce GTX 560 all gave error -97 and Error while computing, regardless of whether they were long or short, with one exception that gave Completed and validated.

The 10 or so on my x64 Windows 7 computer with a GeForce GT 440 all gave Completed and validated, except for one that is still In progress; all short.

Does this mean that I need to set the Windows 7 computer to No new tasks for GPUGRID until you have a newer version of this application ready?

Looks like I'll have to set GPUGRID on No new tasks for a while. 8.41 only wastes CPU and GPU time on my Windows Vista computer, and the graphics board is failing on my Windows 7 computer.

I don't see any particular problem running 8.41 (longs only) on my Win7 64-bit machine on two GTX 750 Ti's (CUDA 6.0). As previously stated in the earlier discussion, it is likely your GTX 560 is overclocked or just too hot, or maybe has failing memory, but that is less common.
http://www.gpugrid.net/results.php?hostid=173205

I don't see any particular problem running 8.41 (longs only) on my Win7 64-bit machine on two GTX 750 Ti's (CUDA 6.0). As previously stated in the earlier discussion, it is likely your GTX 560 is overclocked or just too hot, or maybe has failing memory, but that is less common.
http://www.gpugrid.net/results.php?hostid=173205

8.41 (shorts) worked properly on my 64-bit Windows 7 computer with a GT 440 until the fan on the GT 440 started failing. This appears to be a problem specific to Windows Vista.

I have not found any program for changing the clock rate on the GTX 560, so how could I overclock it? Cleaning the heatsink on the GTX 560 reduced its temperature but did not help this problem. If the GTX 560 has failing memory, why don't I see a similar problem with GPU workunits from several other BOINC projects?

I have not found any program for changing the clock rate on the GTX 560, so how could I overclock it?

I use and recommend MSI Afterburner for that purpose.

Cleaning the heatsink on the GTX 560 reduced its temperature but did not help this problem. If the GTX 560 has failing memory, why don't I see a similar problem with GPU workunits from several other BOINC projects?

From all BOINC projects GPUGrid has the most advanced application for nVidia GPUs. It's using the latest CUDA API (6.0), so it can utilize the GPU to its full capability, while other projects can't (although the GPU usage could show more than 90% under other projects also).