Error when exporting movie

I keep getting an error message (see attachment) when I try to export a movie. Can anyone tell me what this means and how I can fix it?

Thanks,
Susie

Screen shot 2014-03-13 at 3.06.10 PM.png

My problem was because I was using imported jpegs. Here’s what fixed it:

In preferences, go to Import/Export. In the box labled “Import Images” make sure the top square for “Auto Premultiply Imported Image by Alpha Channel” is checked off.

Then re-save your project.