I have an early 2009 Mac Pro with a stock ATI Radeon HD 4870 512 MB Graphics card. When I try and start up, I get grey vertical lines across the screen. It then freezes on startup (progress bar on logo screen). I have tried resetting the PRAM (OPT/CMD PR) and replacing the battery on the board. I have also tried starting in safe mode and have gotten logged on but still have vertical lines everywhere and the computer is pretty slow. Has anyone encountered this? any solutions?