Attached Link: http://www.fleacircus.co.uk/

I am working on an animation of a cannon and used a volumetric cloud to represent the smoke when it fires. I then ticked and unticked the visibility at different points in the animation. When I render the animation as an AVI, the cloud stays behind (see above still from the animation) however when I render a still frame it correctly disappears. Question 1. Has anyone else successfully animated the visibility setting of a cloud? Question 2. Is there an alternative way to do this? My current work around is to put a fade in via a video editing programme.