Desktop Will Not Shutdown Properly After Using Sleep Mode

recently, i've noticed that whenever i sleep my computer, attempting to shut it down later does not work. the process just hangs at the Windows 7 screen with the Shutting down...message. i've let it run for 30 minutes one time and nothing happened, still Shutting down... every time this has happened, i end up manually powering off. the computer shows no ill effects on start up (other than the 'your computer shut down improperly' message). i can't find any unusual events in event viewer, either. it shuts down fine when not having used sleep mode. to sum it up: when i power on my computer normally and DO NOT use sleep mode at all between a shut down, everything is fine. when i power on my computer normally and DO use sleep mode at some point between the shutdown, the computer will typically HANG at the shut down screen and not actually shut down. however, what makes this tough to trouble shoot is that sleeping it for 5 or 10 minutes will have no effect on shutting down...but sleeping it overnight (7-8 hours) will. this problem has been occurring for about 3 months now, though i only started noticing the trend recently. i typically shut my computer off during the week and sleep it through Friday and Saturday and then shut it down again on Sunday (now, i shut it down all the time of course). the computer is virus and malware free according to MSE and Mbam. the only thing i can think of that i installed in between now and 2 months ago were various Steam games and graphics drivers updates. my HDD has never given me any trouble, memory is fine, CPU isn't overheating, etc, etc. my specs are Windows 7 (legit copy before anyone asks), 8gb RAM, 2500k, AMD 6950, Samsung Spinpoint 1TB (regular HDD, no SSD).