Green slides happening on some clips

I've been using Movie Maker for a while now, but I have recently put a clip into a movie and it uploaded as a full green screen. I have no idea what's causing this, and it's starting to annoy me, because it is totally disabling my ability to review certain aspects of my movie and simply enjoy it as a whole. An extra note, the green screen is not always appearing on the clips/time that the timeline suggests it should, it seems that when I put a new clip in, its location changes.