Movie Maker saying “The file is incompatible”?

Hi, I'm a long time user of Windows Live Movie Maker, and I just recently used it all day yesterday, editing my latest YouTube video, and when I first used the software after a long time of not using it in a few years, I decided to take part in the whole Super Mario 3D World Deluxe rumor, and make a fan-trailer for it.

I got to work on it, but stopped after two days. I haven't touched it since. So, I decided to get back to work, but now, whenever I try to open up the project, Movie Maker says the following error:

"Sorry, Movie Maker can't open this project file. The file might not be compatible with Windows Live Movie Maker or be corrupted. Please select a different project file."

I know that the file is compatible, since I edited and saved it in Movie Maker, and I know for sure that it's not corrupted, otherwise, my computer would've noticed, and notified me. And, both my latest video, and the trailer were saved in .wmv form. I have no idea how to fix this. Any ideas?