The 24" iMac 2.93ghz NVIDIA GT120 (early 2009) we use has been working fine until the second half of last year (2010) when the screen suddenly flickers (usually after clicking on safari links quickly one after another, or simply when you click around - does not happen when you leave the iMac alone), then freezes with a 99% chance of non-recovery. However, when you move the mouse, the cursor still moves. Sometimes when we continue clicking at this state, the cursor also stops functioning. Only way to recover is by rebooting, but this problem happens again, usually once every week. We have tried PRAM & SMC reset, also Onyx, Disk Utility and CleanMyMac, it still happens. Disk is verified to be ok. All software updates are installed. Only thing that changed before this happened is we upgraded the RAM to 8gb Gskill brand from the TPC reseller mentioned in one of our Philmug threads, and also upgraded the OS to 10.6.6 then 10.6.7. What could be the problem? Memory? Graphics card? OS Update? Hardware? In one of the forums I googled, the mouse cursor still moving is a sign it's not a graphics card problem. Also read that reinstalling does not remove the problem. I also thought that if it was the memory upgrade, we would have kernel panics instead (doesn't happen). I was about to recommend this for service (under AppleCare till 2012) but I thought that it might be hard to replicate the problem unless they use it as we do, 24/7 room temperature with no air-conditioning (already used SMC fan control but it would not raise the CPU fan rpm, only the ODD & HDD responds; CPU temp usually 51-80 degrees C, graphics diode 63-80 degrees C) & with so many browser tabs open (minimum of 10-20 at a time, maximum about 80 tabs). Having this problem happen about once or twice a week might also mean a long time without our unit as techs will burn it in. I also foresee a long debate with AppleCare hotline and incurring a lot of long distance calls expenses (1-800 does not work for us). Anyone else has this problem or has googled a solution for this? Is this an OS X Snow Leopard update problem?