lurok, have you tried leaving you pc off for a while then trying to play again?, cuz if your pc is anything like my e-machines one, then the sound card may have wacked out and just needed to reset itself.
and before you say it would affect all sound, it wont, believe me,my sound card used to play all sound accept BC's sound, i then turnt the pc off, left it for a few hours or days, turnt it back on and the sound was working like nothing happened.