Ok December 2009 I built a new AMD system. The only part I recycled from the previous system was my graphics card (7900GT). Last week (7-21-2010) my video output suddenly had five columns of yellow dots going down the screen and Blue Screened at the Windows 7 loading splash.
I bought a new ATI 5770 and ran beautifully for 2 days. Now the output is distorted with with overlapping text at the BIOS init and Windows 7 loading spalsh then Blue Screens.
The video works perfect if I switch to the motherboard output. I tried the old 7900GT in a diff computer and it has the same yellow dots and crashing at Windows XP loading splash.
My specs are (nothing overclocked or modified):
Motherboard: Gigabyte GA-MA785GMT-UD2H
PSU: Antec earthwatts EA500 500W
CPU: AMD Athlon II X4 630
RAM: G.SKILL Ripjaws Series 4GB (2 x 2GB)
Well the 7900 is probably toast if its making the same problem in another computer. Did you try your new 5770 in a different computer to see if it works? If the 5770 initially worked and then stopped, something must have changed on your PC, I doubt it would die 2 days later. Try it in a different computer, and then you'll know for sure its a different issue.