iMovie exports "silenced" clip sound

[svdwoude]

hey,
having a little export problem with iMovie.
I made a movie with a collection of clips i filmed, on top of that there's a soundtrack. So I silenced the sound from all the clips, putting the audio volume to 0% (I double checked that).
When I export the movie i hear trough the soundtrack the sound of some random clips...not all the time, it just seems random...

Anybody could give me some tips? Google couldn't really help me... I really put alot of effort in this movie, it would be a bummer if I can't fix it...

thanks a lot!