audio clips won't play a second time

I professionally recorded narration and saved each track as a WAV file so
they could be embedded into the presentation, thus avoiding the hassles of
lost links, etc. This is an automated presentation, with each slide
advancing after five seconds, and then the whole presentation loops so it can
be self-standing at a career fair.

When I place a track/clip on a slide, I tell it to play automatically, which
gives it the property to "play after previous". I then set the effect
options to stop playing after 999 slides. I can listen to the slide show
only once. After that, there never is audio again. Even manually clicking
on the icon and telling it to "play sound" while in the build mode fail to
produce audio again.

If I package it to CD before ever playing it, the CD comes out with audio.
If I listen to it once, then package it to CD, the CD has no audio.

I'm desperate. This presentation needs to be finished and on a plane to
Chicago in two days.