When clicking 'Quit Game' I will intermittently experience system hangs or complete lockup.

I click 'Quit Game' and it goes to a black screen and then if I let it sit there for about 3-5 minutes it will sometimes give me back my desktop, but the system is completely locked for that period of time. I'm unable to Ctrl+alt+del and alt+tab gives nothing, as well. So, without being able to get to task manager I can't kill the process and it's actually faster if I shut down my system by holding the power button and then restarting my computer.

Windows 7 64-bit SP1
16GB RAM
Intel i7-3820 @3.6GHz
nVidia GTX 560 Ti
Asus Xonar DX