My mac pro won't sleep on its own or when I try to put it to sleep.

Question

Hello all,
I have a 2007 Mac Pro and for some reason, it won't go to sleep.  Normally if it was idle for an hour or two, it would automatically sleep but not anymore.  If I put it to sleep manually, it wakes right back up.  I have to shut it down so the hard drives don't spin all night long.  I'm not sure what's causing this.  I tried unplugging all the USB devices and plugging them back in.  It tried resetting PRAM. In my preferences, my computer sleep prefernces remain unchanged from the time that it was functioning correctly.  If anyone has a suggestion I would love to hear it.
The text below is from terminal after typing 'pmset -g assertions'  Perhaps it will be helpful in diagnosing the issue.
5/6/13 11:25:39 PM PDT
Assertion status system-wide:
ChargeInhibit                                    0
NoDisplaySleepAssertion                 0
CPUBoundAssertion                         0
EnableIdleSleep                                1
NoIdleSleepAssertion                        0
DisableInflow                                     0
DisableLowPowerBatteryWarnings   0
ExternalMedia                                   0
No Assertions.
Thank you for your time.
Cheers,
Jonathan

Answer 1

Test after each of the following steps that you haven’t already tried:
Step 1
Take all the steps suggested in this support article.
Step 2
From the menu bar, select
 ▹ System Preferences ▹ Print & Scan ▹ Open Print Queue
Check all printers for unfinished jobs. Deal with any you find.
Step 3
 ▹ System Preferences ▹ Sharing: uncheck all boxes.
Step 4
Reboot and see whether there's any change.
Step 5
Reset the SMC.
Step 6
Boot in safe mode and log in to the account with the problem. Note: If FileVault is enabled, or if a firmware password is set, or if the boot volume is a software RAID, you can’t do this. Post for further instructions.
The login screen appears even if you usually log in automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.
Safe mode is much slower to boot and run than normal. Don’t launch any applications at first. If sleep still doesn’t work properly, back up all data and reinstall the OS. After that, if you still have the issue, make a “Genius” appointment at an Apple Store to have the machine tested.
If sleep now works as expected, go on to the next step.
Step 7
Still in safe mode, launch the usual set of applications that are running when you have the problem, including your login items, one at a time, testing after each one. Some applications may not work; skip them. You might be able to identify the cause of the problem this way.
Step 8
If sleep is still working after you’ve launched all the usual applications, reboot as usual (not in safe mode) and test again. If sleep still works, you’re done, at least for the moment.
If you still have the sleep issue after booting out of safe mode, post again.