My iMac (C2D latest OS etc) seems to wake at random and then fail to sleep after the period set in Preferences. The wake event is recorded as:
Oct 22 21:06:42 upstairs-2 configd: AppleTalk shutdown Oct 22 21:06:43 upstairs-2 kernel: System Sleep
Oct 22 21:06:42 upstairs-2 configd: AppleTalk shutdown complete Oct 23 04:40:01 upstairs-2 kernel: System Wake
Oct 23 04:39:53 upstairs-2 airportd: FastFinder scanning channels again
The computer will stay switched on with this system.log message every two minutes or so:
Oct 23 10:00:33 upstairs-2 ntpd: sendto(220.127.116.11) (fd=23): No route to host
Any idea why it might wake/fail to sleep?