Movie maker video not showing

I can make a movie with movie maker, everything works great.  I save the movie but do not upload as I want to get some audio to add to it.  When I reopen it although it shows all the video, photos and text on the working screen, it will only play the photo's and text.  I cannot play the video content.  Very frustrating as I spend a lot of time making the movie and can see it on the screen as still shots, but the screens are just black when I play them.