Original post by: Dan ,
John - Try 'Check My Temp' from the Mac App store. It shows the internal monitor temp sensors (in my iMac '11 model I have two sensors). My screen is running 67° F & 92° F as I write this. From what you state from the original post your mouse pointer is still moving across the display (correct?) when this happens. If that is so that points me to a frozen OS not a display issue (the displays temp or display hardware). I would first see if you have some malware running. Run Apple's software update or go here if you have Lion without Java running http://www.cultofmac.com/160766/apple-releases-new-flashback-trojan-removal-tool-for-lion-users-without-java/ Also disable Java if you don't need it. I would still get a good virus checker to make sure something else is not running (now or later on). If that didn't solve things I would start by checking the OS and Apps, make sure you have the latest updates running of your apps and any add-ons. If you have any older OS add-ons they may not play well with the newest versions of OS-X (Snow Leopard or Lion) disable them. Also make sure you don't have applications loading on boot. Did you add something new that doesn't play well? If so remove/disabler it. If that doesn't isolate out your issue see if you can boot under an external HD which has a fresh copy of OS on it. If the system does not get crash like before using the external HD apps you can focus on isolating out what is running on your systems internal HD that is crashing it (under that given user account). To isolate out other malware or other background apps from the OS try creating a new user account on your system. Using this account on your internal HD see if the problem persists. If not you have something running in the browser under your original user account. Going into the browser settings fully reset all of it's saved items (Safari > Reset Safari... check off all of the items). Doing this will loose any saved settings so make sure you have written down your web server user accounts and passwords as well as copies of any important URL links. Also remove any add-ins and download and instal fresh copies after you have proven the issue is within your browser. I would also at this point test the HD and defrag it if the drive is very full. You may also need to make more free space so less swapping takes place. Try to leave at least 2-4 gigs of free space on your primary HD. Don't forget to make a backup before doing this. You may also need to boot under an external HD to do a full job. If this doesn't solve it you will need to dig deeper into isolating out the different processes running on your system which is a bit of science and luck using Apples 'Activity Monitor' application. As your system is crashing you will need to have the monitor running on your desktop so it's not covered by something so you can see what was running at that split second it froze up. OK using the external disk did not help now what? If using the external HD did not isolate out an OS or App issue (still crashes) I would suspect a main logic bd has a problem. It could be a cold solder joint on the CPU/GPU logic so when the system heats up it fails. Its also possible the problem it's within a component. At this point I would think about getting it serviced by Apple directly as the first service person (non-Apple? service) did not go down the right path of diagnostics. If you can get your self to a real Apple 'Apple Store' with the system they might cover it under warranty (if the orginal service was done by an authorized Apple servicer) Bring your paperwork and a sad face. You may want to enlist your wife or girl friend to help you here two sad faces does wonders ;-} Good Luck!