I have a 3 year old iMac (21.5'' display). For the last several months, it will randomly start itself up. I hear the hard drive spinning up, and after about 10 seconds, the monitor turns on. I have adjusted the screensaver settings and used the boot disk utilities to diagnose/repair the hard drive and disk permissions. No luck. I can't find a consistent answer to what is going on via Google searching. Any suggestions?