I am trying to load an AVI movie from my dash cam into movie maker to produce a short clip.  The movie loads and I can watch the entire 10 minute clip.  However, when I look at the movie displayed for editing, only the first 18 seconds appear to load and the rest of the movie is shadowed (??) out.  So when I try to take a 45 clip from abut the 6:45 minute mark, I can play it in the maker but I am unable to save it or if it does save, it is entirely black.  What is causing this?