Comment 9 for bug 34947

The same happens if you use anything else to lower the volume to 0 while having the Volume Control window opened. To recreate:

1) Open Volume Control by double-clicking the speaker icon.
2) Open xmms, xine, whatever and set the volume to 0 in xmms, xine ...
3) Try to rise the volume with xmms again.
4) Watch that the slider in the Volume Control window sits down and stays muted.

It seems to me that muting has been added to supress any sound when the slider is at 0. Well, the slider should at least go up even if it would stay mutted. This does not occur when the Volume Control window is not opened.