Amarok & XMMS - Sound problem in Ubuntu 9.04

[saysec]

Hi,
I use Ubuntu 9.04.
For some mp3 player, I didn't like rhythmbox, so I installed Amarok.
I had some problems which I'm gonna tell.
Then I installed XMMS, I again had the same problem.

When I open xmms or amarok firsly, it plays the mp3 or wav files without any problem but while it is on, if I open something else, such as youtube, or facebook video, I can't get any sound from them. XMMS still works, plays, I can get the sound but no from youtube.

Even if I pause, or stop the song in xmms, it still doesn't apply. I have to close xmms, then restart the browser, then open the video - whohoo! I can get the sound finally.

The same thing appears if I first open youtube. I can get the sound, but while it's open, if I try to play something in xmms, it doesn't work.

Could you please help me?

[D-cat]

This is what happens when the soundserver fails to do its job for whatever reason. I find this usually works:
Howto solve all PulseAudio-related issues in Ubuntu|Ubuntu Geek

[saysec]

unfortunately it didn't work. But there is no option on my voice configuration panel such as:
Enable Software Sound Mixing (ESD)

could it be the problem?