I have a 20" late 2006 iMac. Lately, it has been experiencing power issues. For example, if the computer loses power in anyway for a period of time (electricity going out, accidentally unplugged, etc.), it won't power back on. I can press the power button forever, and it won't do anything. No lights. No noise. No beep. No nothing. BUT, if I unplug the power cord from the back of the machine for a few hours, and then plug it back in, and hit the power button, voila! It will power back up no problem. But only after the machine has been unplugged from the back for several hours. Also, sometimes when the machine has been on for awhile (varying time lengths), it will shut off intermittently for no apparent reason. And when it does that, the same thing. It will not power back on unless unplugged for several hours from the back of the machine. I have tried reseting the SMC, I have made sure there is power to the electrical plug. I have tried those things, but am at a loss. Any words of wisdom would be helpful.