iMovie...the Saga Continues

I finally got my video uploaded to TeacherTube, but now it won't actually play.  This is unfortunate, because I'm going to try YouTube now, and it isn't accessible from computers on the Provo School District server.  If I want to show a You Tube video at work, I have to download it at another location first and bring it into class - always hoping that the window doesn't get closed before I want to show the movie.  Since students are often on my laptop, this happens sometimes.