There is a really annoying bug that crops up sometimes in which you will get an error message similar to "xine was unable to initialize any audio drivers" or in KDE 4.2 "The audio playback device HDA Intel (AD198x Analog) does not work. Falling back to ."
To fix this, I would normally reboot, but I found a page that specified how to restart the sound system. The instructions, unfortunately did not work for me, and I could not post a follow up.
$ lsof | grep pcm