Computer won't go into sleep mode

Hi my monitor turn's off but the computer never goes into sleep mode. I've got both my monitor and computer set to turn off at 45 mintues of inactivity. I tried reseting the pram with no success. I deleted the com.apple.PowerManagement.plist file. but it still doesn't turn off, only the monitor. I've set it to 1 minute but only the monitor will turn off. Manually putting the computer to sleep work's fine. Please help.