Late 2009 MBP Refuses to Sleep.

Hello,

Problem: My late 2009 Macbook Pro (10.6.8/Snow Leopard) refuses to sleep. It doesn't sleep when I close the lid and when I attempt to put it to sleep manually, the screen goes dark for no more than two seconds then wakes back up. When I close the lid, I observe the white light on the front right that usually oscillates--dims and brightens-- when it is sleeping. Lately, when I close the lid, the light comes on and begins to fade as usual, but as soon as it is dim it quickly comes back on. It is very similar to someone dozing off and forcing their eyes back open quickly, if a visual is needed.

When I put my ear to the bottom of my MBP, it is still running. However, every 20 seconds or so it sounds as though it is attempting to sleep--the fan and other bits slow down-- but starts back up again. The light on the front verifies this, because it dims then relights quickly when this happens. I have not downloaded any applications that prevent my computer from sleeping. I have enabled settings that put my notebook to sleep everyday at the same time, but it never abides.

Things I've tried:

-Restart (failed)

-Power off and restart (failed)

-Sleep from Apple menu (failed)
-Sleep from power button (failed)

-Sleep from lid closing (failed)

-Sleep from login screen in safe mode by closing lid (failed)

-Sleep from login screen in normal mode by closing lid (failed)

-Resetting SMC (failed)
-Sleep from safe mode after login (failed)

Any help and insight is greatly appreciated.

Thanks for your time. 🙂