[MacDV] Audio Hell

[CFlatow]

Folks,

I have an urgent problem that is making me crazy.

I a trying to export a QT movie from FCE, just as I've done  
successfully, so many times before (as recently as yesterday).
Only every time (about 8, so far) I do the export the movie has two  
empty audio channels.
They are there, but they are empty.

I can play the movie in the Timeline window and the audio works fine.  
The level meter shows a normal decibel modulation as the movie plays.  
The little speaker icons on the two tracks seem to be on in the normal  
manner, and when I export I am sure to note that I am exporting both  
audio and video tracks.

I know that the two tracks are there and empty because when I open the  
exported movie in FCE I can see this. When I look at the tracks in the  
timeline window they look fine (and as I said, play fine).

I just tried to export a different sequence in the same project. The  
audio exported just fine. I can see no differences between the two  
sequences.

What am I missing?

TIA,
Carl