Movie maker full screen blank

I have created a movie using the latest version of Movie maker under Windows 8.1, using photos and video clips from my camera. The movie plays in normal "creation" mode (with the small picture to the top of the screen), but when I move to full screen the photos are fine but video clips show no sound and a blank screen. This happens when starting the movie from the beginning, but if I start the movie a few frames before the video clip, it runs OK with full sound and picture. Please help.