Hi, I have a 24 inch imac computer and it was idle for about an half hour. When i clicked on the mouse, the screen remained black and even after numerous attempts by clicking on the mouse, the screen continued to remain black. I finally clicked on the power button and the computer turned on. I would like to add that this computer has had a power supply replacement this past April and two days after this part was replaced, the same issues that I've had before this part was replaced, have continued, as well as others such as a loud noise when attempting to insert a cable into one of the ports. I would apreciate any feedback from members who have ever experienced their imac suddenly shutting down, when computer was idle. Thanks!