I've been having this problem for a while and it started when I wiped my computer clean and reinstalled Windows 7. When I installed Sony Vegas I noticed every time I load up Vegas that it kills any audio that's currently playing. Skype, Youtube, twitch, Windows media player, everything.
It does this when the audio engine is being initialized I think, from what I see with Windows media player it says "An audio device was disconnected or reconfigured. Verify that the audio device is connected, and then try to play the item again." If I have headphones in when I start Vegas up it doesn't do this.
I actually uninstalled Vegas pro 12 completely registry and all several times to see if this would fix the issue with no success. Does anyone know how to fix this?