My 2011 entry lvl 21" imac has started acting badly. It will power up okay and stay on for 10 minutes or a bit longer then the screen wil switch off. There is still power running through it as my hub light is still on but screen will not power back on. Its not gone to sleep and neither key press or mouse click work only holding power button until i hear it switch off and press again to start then hopefully get another 10 minutes or so. Power settings are set to normal so thats not to blame and the same happens when i boot either into bootcamp or osx. I dis read of something similar and if i have a program running such as itunes in the background it does seem to stay on longer but eventually will go off on its on. I can only think its some kind of hardware problem and the bad news from my point is the one year gurantee from pc world ran out 2 weeks ago and i never got applecare Anyone heard of this or know from my garbled ramblings where the problem might lie? As usual any advice appreciated.