In System/Prefs/Sound menu, changing the Sound Events, Music and Movies, and Audio Conferencing to the PulseAudio Sound Driver, fixes YouTube videos in Firefox, but breaks Amarok, which gives a "Xine was unable to initialize any audio drivers" error message.
In Amarok, there does not seem to be an option to the set the output plugin to PulseAudio.
I have this problem too.
In System/Prefs/Sound menu, changing the Sound Events, Music and Movies, and Audio Conferencing to the PulseAudio Sound Driver, fixes YouTube videos in Firefox, but breaks Amarok, which gives a "Xine was unable to initialize any audio drivers" error message.
In Amarok, there does not seem to be an option to the set the output plugin to PulseAudio.