Why won't my WMM movie let me publish?

Everytime I try and publish my movie on Windows Movie Maker, it says that it is unable to publish it, and I must check to see if I have enough space on my disk. The disk has 448 MB free of 28.7 GB, and the movie takes less than 20 MB up. It also says to look whether or not the place I am trying to save it to still exists; I tried saving it to multiple places (videos, pictures, desktop, etc) and they all exist, it just won't save. I've tried their website and other help websites and nothing is helping me. I need this published ASAP - what am I supposed to do?