The reason you're not getting a moving background is because you need to be looking through a camera. That, and you need to set the Starfield up to use the camera.
believe it or not, I was.
I used a camera to render two different frames spaced 5 frames so the motion was evident. and the background was still freezed.
I temporally fixed it: a BIG sphere with stars.tga in 2-sided map. I know, bad work there.....