Recently my 24" iMac 2009 started freezing every 60-90 minutes. I can still move the mouse, but nothing seems to respond anymore. This is what I tried so far: Disconnected all external devices Tested the RAM memory by removing them both 1 by 1 (as well as running a memtest Reset the SMC (e.g. but power for a while) Reset the PRAM Started in safe mode (still crashing) Tried re-installing OS X. First few times that didn't work (crashed during setup, after a few times it got installed but still freezing). Temperature of the CPU never goes above 40 degrees. All other items are cooler. Tried to run the hardware test, but that doesn't seem to be installed on this OS X (so haven't been able to run this test). Any thoughts on what you think might be the problem? Any kind of help would be very much appreciated!