I upgrade my 2009 Mac Pro Quad Core 2.66, (4,1) video card to the Ati Radeon 5770. The card worked fine for a few months but recently started making a lot of noise. Now every time the noise begins it stalls my computer for a couple of seconds. My Mac Pro is at the Apple store right now getting a full diagnosis. The dude at the "Genius Bar" told me there could be compatibility issues. Ill find out in the next few hours. Anyone else run into the same problem? Thanks!