Sound fade out problems

Dear colleagues,
I have created an animation to which placed a sound track. It doesn't last more than 10 secs.
I keyframed the sound track, but when I export the project as a Quicktime movie, the fade out that I made to the sound using keyframes, works in Motion, and the sound fades beautifully in Motion, but not in quicktime, the music simply is not fading in the resulting quicktime .mov.
it just keeps the same volume till it ends abruptly,
any ideas on how this is solved?
Using Motion 2 on a Panther environment.