iMovie VoiceOver Giving Off Error Sound?

I don't believe I did anything wrong, but the voice over feature in iMovie hasn't been working for me. It happened in the middle of a recording, I had stopped recording to start another segment, and the little microphone icon vanished. I went to Window/Record Voiceover, it showed up again, but since then, every time I click on it it makes the error sound. Please Help! Thanks, Daniel