suddenly I have no sound available on my system. I played sound earlier today, but suddenly I get nothing. I have not changed hardware, not rebooted, I did not install any software until after the problem started.

If firefox is using sound, I have always had problems playing other sound, but now I cannot use sound even if firefox is not running, so ff is innocent.

I checked the multimedia section in system settings, and find two sound devices: nvidia ck804 and pulseaudio (in that order) and if I press the test button while selecting either, I get this message from phonon: "the playback device <DEVICE> does not work, going back to ." (fast translation).

I know this question could be placed in hardware as well, but I am almost certain it is caused by software.

seems like the problem is at least partially fixed, but I do not know how...