Couple things to check... first is your face normals on your objects, either turn off 2-sided lighting to check, or turn on display face normals.
Try rendering just a single frame, with and without the lights in your scene (try using the default light to see if that's the problem).

Also, you shouldn't really render out as an avi... it's better to render out indiv frames and then combine them in something like premier or final cut or after effects or virtualdub.