PowerPoint 2008 QT movies end prematurely in presentation

I just converted from PowerPoint 2004 to PowerPoint 2008, and things are
generally ok *except* for this:

My QuickTime movies end prematurely when played... it's like PowerPoint
decides to edit the last 1 or 2 seconds of each movie and does not play
it.
PowerPoint 2004 did not exhibit this phenomenon.

Any ideas?  Your help is GREATLY appreciated... thanks in advance!  Peace!