It seems that the problem is deeper. After several hours, suddenly not only there was no sound but even media players (Totem, Gnome-MPlayer, SMPlayer) couldn't play videos (ffplay played videos without audio).
Logging out of Gnome and logging into IceWM didn't do anything but GDM had its system sound working. Only killing and restarting PA solved the issue. I couldn't find any error message. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org