Here's a simple story as to what's going on with my computer.
I haven't played SC2 in a long time. I decided to play again. I'm listening to my playlist of music. I start up SC2. My music stops playing. I minimize SC2, music player says music is still running. I alt f4 out of SC2. I can hear music again.
I start up SC2 again. Music stopped. I go to sound options in SC2, and I mess around with all of the settings, and still get no sound. I join a game, still no sound. I alt+f4 SC2. I hear my music again.
I use Windows 7, I use a lenovo laptop, all my drivers and updates are up to date. This has been going on for about 2-3 months now.