Comment 38 for bug 385344

I saw your comment and it seems correct to me.
However, I couldnt find a way to do so easily. I don't know how to make pulseaudio change my sound card.
- "startup - sound & video - pulseaudio device chooser" does not produce anything
- "startup - system - preferences - pulseaudio preferences" does not give me the list of hardware, only network informations.
- gnome-volume-control applet does not allow me to change the hardware informations.

So, I am quite lost about what I can/should do. But I think you may be right about the sound reason for this bug.