I only tried in Quakelive, SC2 and Call of Duty 4. I didn't notice any black spots in those games. However, the pace is those games much faster and I could have missed it? This is very annoying. It is a driver or coding issue, I will be very surprised that I am the only one experiencing this because 58xx is a popular card while SC2 is a popular game.
I do have other applications running in the background, but I tried running it alone and it didn't make a difference.Another example