Comment 9 for bug 356687

It seems to me, that playing flash video (youtube) is handled by $HOME/.mozilla/plugins/libflashplayer.so. This file is quite old (from June 2007), while the problems began with Ubuntu 9.04. My conclusion is that installation of flashplugin-installer might be a workaround, but not a solution of the root cause.

I think I remember some problems related to pulseaudio when I tried out Amarok (music player). I can't confirm right now, because Amarok has no setting of it's own that selects pulseaudio or some other mechanism. But I supports that this problem is related to pulseaudio.