Computer doesn't like to sleep.

Hey there. I have an issue where even though I have all wake timers turned off, and I have it set in Windows to sleep after 10 minutes, the computer simply refuses to sleep. Unless I click the sleep button, it will not sleep. This really bothers me as I am a volunteer firefighter, so when I get a call, I just get up and dart to the station, not worrying about my computer. But I really don't want it on for a long time. I've been on calls where it's been 6 hours until I got home, and my computer was STILL awake. My cat can't mess with it, I know that for a fact, so she's not keeping it up. I'm not sure what's causing this, anyone know? I'd love to get this fixed, thanks in advance.

Specs:

Motherboard: Gigabyte 880GM-D2H
Processor: AMD FX 6100 Black Edition
RAM: G.Skill Ripjaws 8Gb, Dual Channel DDR3
HDD: Seagate Barracuda 1.5tb Green x2
CD Drive: LITE-ON DVD R/W
PSU: Corsair somthing or other 80 plus gold
OS: Windows 7 Ultimate 64bit (installed on 256gb ssd)