Wife's 2007 24" 2.8 ghz 6GB RAM running SL, and now Lion.
For the past month or so, It won't automatically shut down at night per the schedule in System Prefs/Energy Saver pane. My wife may not use the iMac for several days at a time, and then use it daily for a week or more - very random.
I've changed the settings by minutes, by hours. I've Safe booted.
I will try logging her out and logging into my account tonight to see if it performs there.
I do have a current clone and TM backups on an external drive.
Other than a complete reinstall of SL then Lion, what prefs are there and where are they that I could delete and re-establish to fix this problem?