Here is what just happened... I just received my refurb 2.8Ghz 24" iMac today. I have been setting it up and transferring files to it for the last few hours. I just installed 4GB of RAM from Crucial to upgrade from my 2GB that came preinstalled. I opened Hulu and started watching a video full screen while I was working on something in the same room. All of a sudden the playing video froze and there was a loud high pitched squeal coming from the speakers and some crackling, followed by another high pitched squeal from the speakers and then the computer froze. I know it wasn't a fan noise or a hard drive noise, it was definitely a high pitched audio tone and crackling from the speakers when it hung up. The only way I could make it stop is to hold down the power button and turn it the iMac off. Has anyone had this problem or heard of this problem before? EDIT: I wonder if it could have been my photo collage screensaver kicking in while the hulu video was playing fullscreen that caused something to lock up? It seems like it was in the timeframe from when I walked away from the computer to the time it crashed.