Only Sound No Video

So I go into video editing, I add a movie, an AVI file. I drag to frame one. Then I add an audio file drag over to top channel. The video is 285 frames long and the audio is a lot more, (I don’t know how long). So I set to:

HD720p
Output: Xvid
Encoding: Format AVI, codec MPEG-4(divx), and Audio: MP3.

I click Render Animation, 30s later i have a black video with only sound? What the heck happened? :eek:

Thanks in advance.