I have my older iMac in the kids room and basically powered up all the time. I notice that it is asleep by the pulsing white light... today I went past and noticed no light... wiggle the mouse, tap the k/b and sure enough no wake up that I am used to. I pressed the power button and nothing... I pulled the power cord, re inserted it and tried again.. nothing! I left the power cord out of the back for an hour or so and just now it powered up OK Any ideas?