Thanks - I'd already matched the frame rates of the AVI and the animation, and it's still not moving as expected. Every second frame is rendered twice, as follows:

Instead of rendering frames 1,2,3,4,5,6,7,8 etc of the AVI in frames 1,2,3,4,5,6,7,8 of the animation, it renders frames 1,1,3,3,5,5,7,7,etc of the AVI.

I know this because I created an AVI with numbers 1-25 in frames 1-25.

Is there some setting I have missed?

Thanks,

R