I just upgraded from a gtx260 to a gigabyte gtx 560OC link shipped from newegg a day ago. It worked fine out of the box in windows, so I installed the 266.66 drivers for win7 64 from nvidia's site and started a game (final fantasy XIV).
The game crashed to a cobalt gray screenafter a few minutes, from which I had to do a hard reset to get out of. After about 3 minutes in any directx game (directx 9 or 11) it outputted a cobalt gray screen (not the BSOD).
kind of like this color
I removed all nvidia drivers (display, hd audio, physx) and used ccleaner to remove any nvidia registry settings, then reinstalled the 266.66 drivers.
The games I tested (FFXIV, Aliens vs predator directx11, fallout NV) again all crashed within a few minutes, but this time I received the following error instead of a cobalt screen:
"unable to detect directx device"
As a last resort, I used the drivers that came with the card's driver CD, 266.44, but I got the same "unable to detect dirextx device" error.
Not just Gigabyte but is a symptom of a larger problem as a result of the economic depression. To maintain profits manufacturers have cut corners on quality more than they have before. Compare a card made during the Geforce 8 and 9 era to a card of the current era you would notice that quality in general has decline in several areas. The Fermi line has suffered heavily as well the same for ATI's offerings.
When it comes to Gigabyte cards you may have to mod them and are not meant for the newts of the computing world. I modded my Gigabyte GTX 460 and it already has close to 2k hours of use.