I'm running FC6 with a gnome desktop and find the sound going out intermittently. What this means is that applications like xmms give the message "Please check that your soundcard is configured correctly" and the volume control widget displays only the microphone. The one way I've found (so far) to get around this is to open system -> administration -> soundcard detection -> system -> reload audio drivers, which then requires a reboot before the sound comes back on.
