Have you guys noticed this? Whole system locks up when you add/ remove/ change headphones a couple of times during an in game, engine rendered conversation. Pretty cool. I remember getting this during the beta also.
my guess is that it binds itself to the device that it originally starts up with. My thoughts as to why would be because of online chatting during gameplay. It binds itself to what it thinks might be a mic and speaker combo (unless there is a stand alone mic). When you unplug it, it looks for a device that is no longer there, and doesnt have a refresh/change source type of program. But who knows.
A LOT of games do this; the problem happens due to taking control of the audio devices in windows, then when the device is no longer there and you try to access the hardware...not pretty, let me tell you.
If you want to enable/disable a device, do it through the Windows Control Panel; pluggin in/unplugging USB audio devices while in game is asking for trouble, especially unplugging the current output device...