GStreamer was unable to detect any sound devices. Some sound system specific GStreamer packages may be missing. It may also be a permissions problem.
The error messageI was getting. I installed a few things for testing. Something broke. I googled for a solution without luck.
XFCE4 mixer was greyed out. I couldn't use it. I could use AlsaMixer. I could get sound using MPlayer. I could get sound using Audacious.
I tried to remove gstreamer using aptitude without luck. As root I deleted gstreamer files and directories:
rm -rf /usr/lib/gstreamer-0.10
I tried aptitude again:
aptitude remove gstreamer0.10-alsa
This time it worked. I got:
root# aptitude remove gstreamer0.10-alsa
The following packages will be REMOVED:
0 packages upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
Need to get 0 B of archives. After unpacking 578 kB will be freed.
(Reading database ... 91754 files and directories currently installed.)
Removing gstreamer0.10-alsa ...
I purged gstreamer0.10-alsa and installed it again. It worked. This time audacious didn't complain when I fired it up. XFCE4 mixer was stilled grayed out. I removed it from XFCE4 panel and added a new XFCE4 mixer.