[Daniel Carmo]

I had the same problem.. I’ve noticed that the master track have only one icon of “sound” (like mono or something) and other tracks had two (like stereo)! After had tried many things with no good results I created a new sequence, and that new sequence have the master track with “stereo icon” so I copied all objects of the other sequence to this new one and it has solved the problem of exporting the video! =)
Hope this helps!