When I start up New Vegas, and alt-tab out and check my volume mixer, it says that it's at around 50% I cannot change this using the slider, it's stuck at around 50%. After awhile of playing, the volume will drop down to 0% (This happens instantly if I go indoors) I have tried, restarting, reinstalling, changing the in game sound settings, fiddling with the .ini settings and nothing works. Please help me.

Also I forgot, when the sound goes down to 0% if I get into combat and the combat music starts it will go back to normal, and when combat ends it will go down to 0% again.

Anyone? Could really use some help here.