My Mid 2010 iMac i3 3.2Ghz 4GB RAM overheated yesterday. It turned off and would not turn on again. I waited about an hour and tried again and it turned on for about 5 minutes (fan on 100%) and then it shut off again. I'm running OSX Lion 10.7. The only hardware that I think could have any bearing is a M-Audio Firewire 410 sound card. I have a FW800 to FW400 cable to connect it. I only had Safari, iTunes, Chrome and MS Office 2011 open at the time and was not using the computer. Has anyone had a similar experience? Or do I have a lemon? I also have the issue of dust within the glass (grey spottiness), has anyone been able to resolve that issue? Thanks.