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I was getting similar errors for my 8800GTS and there is a HUGE thread on the nVida forums somewhere all about it... the drivers were causing the problem for 99% of people. nVidia was forced to make a public statement about it that they were working on the issue... Also it seems the old drivers weren't being removed or overwritten properly so most people have been using drivercleanerpro or similar in safemode, then installing new drivers in safemode and rebooting. With the latest drivers I no longer get the errors (after using driver cleaner)... BUT, I did also have some dodgy RAM that could have been a contributing factor. But not sure why RAM would cause a GFX error?
Just a FYI, I was dual booting Ubuntu Linux and never got a single error with the Linux drivers, even if my RAM may have been dodgy at the time.