Hope someone here can help. I've been reading things all over the Web for at least the past week on this and haven't found a solution for my problem. Basically, my Mac Pro (2009 octo 2.93GHz), which is just over a month old [gave up waiting for 2010 models] won't go to sleep by itself. When I first set everything up, the computer would sleep by itself like a proper little trooper. The problem seemed to start after I installed a Sonnet Tango FW800/USB PCIe card, even though Sonnet claim that that card works fine with Mac Pro power management. Even after I've removed the card, the computer still won't sleep by itself. I deduce therefore that the card wasn't the problem. At the moment I've unplugged all peripherals apart from the USB connection to my ACD to connect to the keyboard and Logitech mouse receiver. I've turned off Bluetooth, turned off Wake for network access, turned off all sharing services. I've reset the NVRAM and the SMC. I've booted into safe mode a couple of times to run an automatic fsck and clear the various caches. Nothing works. The computer won't sleep by itself. I've tried both PleaseSleep and Lights Out. Neither works, and, incidentally, they both strike me as hacky, undersupported apps. I've tried quitting all open applications and leaving the computer but it still doesn't go to sleep by itself. The screen turns off when it's supposed to, but the computer never sleeps. I've got 16GB of OWC RAM installed, and hard disks in all four bays. But the computer used to sleep with this configuration. Like I say, I've now taken out the Sonnet Tango PCIe card in an effort to isolate the problem. Can anyone give any suggestion to fix this? I'm reluctant to start reinstalling everything but I wonder if that won't just be less time and effort than everything I've gone through so far. The computer is set to wake up every night to do a local mirror backup (SuperDuper) and network backup/sync (ChronoSync). It's really irritating to find it still wide awake when I come to it later in the day. *Insert typically over-blown comment about 'so much for just works' or similar* Help me MacRumors, you're my only hope. Seriously, most other forums about the place are pretty rubbish.