Monitor shuts off but computer still running
Sometimes with no apparent correlation with internal hardware temperature my iMac screen shuts off, but the computer itself still running (I can type something, use it...as usual, but the monitor is off. I can see my desktop if I point it to direct sun light).
I've tried to restore the original configuration but it's the same.
There is not an exact delay time before shuts off; it can happends some minutes after startup, some hours later or some weeks later.
To restore it I need to put it in stop (with the power button) then press it again to awake it. It turn on again without any problem.
iMac 27 Mid 2010-Intel i3 3.2-2GB DDR3 Ram, OSX10.8.2,ATI Radeon HD 5670 512 MB.