While Linux marches ever closer to being user-friendly, there are still a few loose ends to be tied up. Networking continues to be a bit of a sticky spot, and Bluetooth support is definitely in need of some refinement. But another area, and one which you would expect to have been tied up nearly by now, is sound. The PulseAudio server can help you take care of this problem, but simply installing it doesn't clear up the problems with programs taking the sound card and never letting you have it back.
PulseAudio is an audio server for Unix and Windows which provides software mixing of audio streams, audio output duplication, et cetera.