Why won't my iMovie upload to YouTube?

I'm using an iPad2 and OS4, and when I export my iMovie and attempt to upload it to YouTube, the blue progress bar goes all the way to the right, but the window continues to say that the movie is uploading to YouTube. It doesn't matter what resolution I'm using, and the video is less than 2 minutes long. I'm stumped. I'm a teacher, and several of my colleagues are having the same problem. I've had this problem both at school and at home over Wi-Fi. Please help.