Weird: No suitable graphic devices found

I get the above error message when I try to startup Solitaire

I have a dual boot Vista system 32bit / 64 bit.
In 32bit Vista all is ok.

You will say: so what? Who needs Solitaire? But I want to understand/fix as nobody knows which type of problems I could encounter next.

System: Intel 8400, 8 Gig mem; Nvidia 8600GTS; Vista64 SP1
Analysis done:
- Vista says: performance level 5.6 so OK it recognizes the card.
- System> Device mgr>Display adapters : all ok (no problems found in the driver section).
- Run Direct10 diag: no errors found

Don't know if it worked before SP1 (never tried out a game)

What else should I investigate?
TX - Alfred

Reinstalled Nvidia.
Don't know why but I also needed to deinstall Adobe PDF reader (went back in time with System restore). All OK now