Comment 29 for bug 383756

The update unfortunately doesn't fix it, the behaviour is the same as in comment #26.

Bug 387866 seems to describe the lack of separate control from external (docking station) versus internal speakers (as does this bug report) and a general lack of sound on the headphone jack of the docking station, which I don't experience. IIRC, there was a moment in 9.04 development where the headphone jack of the docking station didn't work at all, but the last time I checked it was producing sound in 9.04, just not offering the option to disable the internal speakers or doing it automatically.