I have the most annoying problem with my 8-core 2009 Mac Pro running OS 10.9.5. About 50% of the time it refuses to sleep - it goes through the pre-sleep cycle and just as it should sleep the fans boost and it restarts. There doesn't appear to be any pattern to when this happens - i.e. how long it's been running, what apps are open or have been used, what network activity is going on, etc. I've tried all the tips picked up on the net to search for the process that's keeping it awake (terminal searches) but no luck. It's affecting my work. I use it for music production and need to be able to use it when inspiration strikes but really don't want to keep it running 24/7. Any suggestions really gratefully received.