hi all,
i've set my mac pro to sleep after 30 mins of inactivity, which it does, but within 20 seconds of sleeping i hear the hard drives and fans starting up again, it runs for about another 20 seconds and then sleeps again. this cycle repeats indefinitely - very annoying.

i've often gone to bed and this cycle is still going the next morning! one odd thing, when i put it to sleep manually with command+opt+eject this problem does not occur, it only occurs when it auto sleeps using the energy saver.

i tried disabling the "wake for ethernet..." option but this doesn't help.
could it be something to do with my usb hard drive which i leave attached?

anyone have any idea what causes this and how i can fix it. currently i'm just putting it to sleep manually to avoid this.

thanks in advance for any suggestions.

For clues as to what's happening, bring up the console app and put a mark in the console log before the sleep/wake cycles begins. Then, after a few cycles, you can examine the console log for any errors/strange messages.

Hope this helps.

This also happens on a real Mac? Strange .. I got the same problem on my hackintosh. Up to now I thought the Nvidia 7300GT would cause this...