I actually have been living with this problem since I purchased the iMac from day 1. I never really had the time to find the root of the problem, although I guessed it was probably because of some software. So here's the problem: 1) Display dims and turns off properly at the correct time, but 2) the iMac never actually sleeps; you can still hear hard drive noises and, upon moving the mouse the screen immediately turns on with 0 delay, with all the networking apps still online (compared to a normal Manual Sleep, apps like Adium and Skype logs off). 3) Computer goes to sleep correctly if given the sleep command manually. Yes I have: 1) already Repaired Disk Permissions. 2) already Reset the SMC. 3) already tested on a brand new user account; problem persists. 4) tested with all applications off... 5) tested using SMART Utility, screenshot here: There was another problem with this HD, when iMac arrived out of the box, it wasn't able to allocate 40GB for a Windows Bootcamp partition. Which was kind of weird, I know. This is starting to look like a hardware issue which has me worried. So what should I do at this point? I don't really have the time to send in my iMac for an extended period of time, as I do need it for work.