Clip is shortening when saving MM project to .avi file

Hello! I saved my MS Movie Maker project into a movie file (DVD-AVI), but
during playback of this file, some of the clips later in the movie only
display briefly, followed by black screen for the remainder of that clip.
The clips at the beginning of the movie look fine. Same thing is happening
with some still pictures (.jpg format) . . . OK during the first part of
movie, blurry during the latter part. Any ideas as to the cause?
--
Barclay