Windows Movie Maker

Hello,

I am trying to create a senior class video for an upcoming graduation in Windows Movie Maker PRO. I purchased and downloaded this app, and have had very little problems using it. However, once I saved the movie, and tried to open it again, it only shows three image clips and fifteen seconds of a video that was previously almost fifteen minutes long. A similar issue occurred yesterday, and it resolved itself without my intervention, so I know that the full video is saved, or at least more than the three images it is showing me. I need help recovering the video that is there. This cannot happen before graduation either, so any tips for preventing this issue?