MBP13: Sound dies after a few minutes

[roblin]

I have a 1month old 13" baseline MBP running snow leopard. Today when I watched some 720p movie the sound died. Same with all programs. A reboot and it worked again. Then after maybe 20minutes it died again.

My sound settings looks like this:



Any ideas?

Edit:When I switch between 2channel x bits I heard a sound.

 

[roblin]

If I plug in 3.5mm headphones they work and when I plug them out the laptops built in speakers are working again.