Movie Maker Error: file not compatible or may be corrupted?

I've been using movie maker for about two weeks now working on one project and suddenly today it started malfunctioning. At first it wouldn't let me split a clip and then would freeze after I tried to do so. Now it isn't letting me open the file at all, saying that it isn't compatible or that the file was corrupted. I don't understand what has changed-the only thing I've changed is added a new clip that I filmed on my phone. But even after I added the clip it was working fine for a while. I also have the latest version of movie maker so I know it's not an updating issue. What's going on? I need to have this project done by Friday, so what can I do to fix this?