Sound on/off button plays different qualities first and second time

I just made this button in the top right corner:

http://www.hottvnetwork.com

It works fine, except the first time it plays the music file the quality is really bad, and then if you stop it and start again it sounds fine. Why does it act like this and how can i fix it?

What's the source of the music? For example, is it internal or external?

the music file is embedded in the .fla

Now I can't find the audio link on your website.