.fla to .mov export - .mov ends prematurely

I haven’t used flash in years. I’m using CS3. I made a video of a static image and added 3 1/2 min of music to it, all in the timeline. When I save it as fla, it’s the correct length, but when I use export>quicktime, the final .mov result is only 17 seconds long. Any ideas why this could be happening?
thanks!

I had this happen with another program, and the explanation I got was that I had to buy some kind of proprietary plugin for it to produce the full version. May not be relevant here, but sounds very similar.

Can’t remember exactly what cs3 can or can’t do, but you’ll need the root timeline length in frames to accommodate the entire 3 minutes of music (i.e you should be able to see the audio waveform in its entirety) to correspond to the expected quicktime length.