Because 157/300 Isn't close to high enough to run 3 monitors. So what happens is that the CCC keeps jumping from the 157/300 to the OC settings, in my case 756/1000. Every time the CCC jumps back and forth the screen glitches and artifacts. This jump happens several times a second. It's been a known issue with the 58XX cards and multiple monitors for what, two years now? Still no fix, or even acknowledgement, from ATI. Used to be able to fix is by manually tweaking the profile, which was a pita but at least it worked, but now ATI has apparently killed the ability to do that too. I'm Nvidia from now on.