Comment 18 for bug 296738

The problem seems at least partly to be a PulseAudio problem maybe a consecutive problem though.

The problem as mentioned earlier here is that some sound channels are muted and most handles reset after a reboot but not at a re-login. After adjusting the main sound handle then Totem sound works but not e.g system sound, vlc sound, etc. Using the mouse pointing at a system sound e.g in directory /usr/share/sounds/ubuntu/stereo works but not playing them under System/Preferences/Sounds.

However after adjusting the main handle for sounds AND removing the directory ~/.pulse everything seems to work until a reboot or re-login where this directory is recreated and thus has to be removed (workaround) again to get all sounds and sound apps working.