I had the same problems as described by Anders Häggström & kede.
So, with the speaker-test command I could hear sound and it was silent for other programs.
For me, the bug was solved by restarting the pulse audio server. I was planning to isolate the solution, because I tried several things. However, even after a reboot, the bug did not appear again :-D. So probably, these commands are the solution (for me at least):
I had the same problems as described by Anders Häggström & kede.
So, with the speaker-test command I could hear sound and it was silent for other programs.
For me, the bug was solved by restarting the pulse audio server. I was planning to isolate the solution, because I tried several things. However, even after a reboot, the bug did not appear again :-D. So probably, these commands are the solution (for me at least):
$ speaker-test -c2 --device cards.pcm.iec958 --rate 44100
$ killall -9 pulseaudio
$ pulse-session
I'm running Ubuntu 8.10, 32 bits on a Asus M2A-VM motherboard with 690G chipset and a Realtek ALC883 audio chip.