SR-71 Blackbird said:
make sure you set your sound defaults in your audio control panel!
the sound defaults are set right. the problem does not appear when I play music (iTunes), only when I open a video file with media player classic (also windows media player). opening the video 5 or 6 times restores the sound eventually. I also have the problem with some games (e.g. Grid).
I think it has something to do with the older sound blaster live drivers,but I can't find newer versions of the driver.