Ok, problem solved for now. It is clearly a hardware issue with my Gigabyte GeForce GTX 460.
Solution: Open case, remove graphics card, blow dust from all fans boards, etc. (it wasn't
too bad, but definately dusty), carefully wipe PCI connector, re-seat card.
All better. Now . . . . will it stay fixed?
I'm looking at a System with a GTX 460.
Has your 460 been behaving?
I'm wondering if it will work ok since it's not a PPro-approved card.
I'm using a GTX560 which is almost identical to the GTX460. Its been smooth, if that helps.
My 460 has been working just fine for over a year.