I recieved my replacement 24" iMac on Monday. I returned it because I was gettting kernel panics and didn't know why. Applecare was unable to resolve the issue so they sent me a new one. Well, this one did it too. Same problem with the exact same cause. To make a long story short, it was only my Airport Extreme base station. It just needed to be reset. At least this new one doesn't have any dead/stuck pixels. The last one had about five of them in a little patch at the bottom.