Currently Being ModeratedDec 9, 2012 8:24 AM (in response to Xlim17)
See here about fixing grey screen at startup.
Did you add any ram recently?
If yes, it could be incompatible ram.
Remove it and see if the iMac will start.
Any new peripherals?
Unplug anything that is connected to the iMac and see if it will start.
Currently Being ModeratedDec 10, 2012 3:37 PM (in response to Stela)
About 105 degress. I have yet to try reinstalling the OS. I have Mountain Lion 10.8.2 installed. Which OS do I install from scratch from, SL?
I actually turned off all applications but it didn't help.