Windows Vista Problem with sound output

Hi,
I am posting here because I have a problem with my audio in Vista.

I usually let my youtube videos load in background while I am listening to some songs. Sometimes this will work perfectly (I am listening to MP3 files while having the video paused), but almost all the time I receive a message that states that there is a problem with my sound card, and therefore I can't play any files on WMP or WinAmp; but the videos will still play perfectly. And when both things work at the same time, the audio files take a lot to start.

Does anyone of you know why could this be happening, and what should I try? I am using a laptop with a VIA "High Definition Audio" soundcard (I seem to not be able to retrieve a code or number) in Home Premium edition.

Thanks!