Nan means “not a Number”, essentially infinity. Some NaNs are normal. A long string of them could indicate a failing component, often memory.
Every post I saw on a couple of forums referred to the NaN occurring when overclocking on these work units.
A long tine folder recommends using StressCPU2, since it uses GROMACS to abuse the CPU. If it can handle StressCPU2, then it can handle F@H.
I used to have stacks of nVidia cards but switched mostly to ATI for the folding. nVidia is finally working with F@H but it is still many months out.
I did run stressCPU2 on my folding machine and it ran for 24h without errors. I will try to start it up again b/c it just may be the new projects.
However, my new PC which I have overclocked will also run stressCPU2 just fine, but will not even complete old WU’s like the supervillans. The OC is stable with everything else, so I just don’t use this one for folding. One day I will take it back to stock setting just to see if it was the OC. This is the machine I have the nVidia 8800 on which I wish I could use.