Sound button - Anomaly

Hello. I’ve got a sound button with a mind of its own, and wanted to see if anyone could help. My menu is sat on the stage, and along with it is a movie-clip with a sound on/off button and an mp3 that starts playing as you open the site.

However, for some strange reason the audio is triggered by my menu navigation buttons as well. Its almost as if the navigation buttons are simultaneously controlling the main timeline and the mc timeline, even though I don’t want this to happen.

Any clues?

Website is here:
Fla is here:

Many tanks.