Why does my mac go to sleep and not wake up?

Question

I have a 24-inch, Early 2009 imac - Processor  3.06 GHz Intel Core 2 Duo - Lion OS
I used to be able to leave the machine on, it'd fall asleep and I'd awake it by touching the keypad or mouse.  Now the machine goes to sleep and I can no longe awaken it.  I press the power button in the back and display turns on but no mouse.
Any ideas???
Stuck in NH.....

Answer 1

G B-D,
A cluster of recent occurrences suggests that it might be a software/firmware issue. (Have you performed a firmware update recently?) However, if it were my computer, I'd want to make sure it's 100% before your window period ends.
First, I'd try fixing the problem with the list of suggestions from the attached link. This includes every solution I've found relative to this issue.
Second, I'd document the problem. That way you can determine then it happens, under what conditions, and how you can avoid it. For example, using a key sequences like CMD-Option-Eject should safely sleep your computer, hopefully avoiding the problem you note. Other users say that rebooting several times in a row clears thing up.
Third, once you have your documentation, and you done several things, and there's no solution, you might think about visiting your Apple Store; it's a lot easier to carry around a MacBook, but I'm not sure what your options are.