Comment 33 for bug 417778

Just one more observation: xfce4-volumed opens all mixers on startup, then chooses to use only one, but it doesn't bother to close the other mixers. This behaviour could be improved to avoid wasting resources (btw, this would actually also fix the problem in some cases where the problem is triggered by unplugging a secondary sound device like a USB headset that's not being used by xfce4-volumed).