VS8 Pan & Zoom changing aspect ratio?

[songsmith]

Just downloaded the trial version of VS8, and I love it. My first time working with a program this advanced (previously have used stuff on the order of Windows Movie Maker), so maybe this is a stupid question, but I'll ask anyway.

I applied the pan&zoom function to several stills in a project, and when I did a preview of just the clip, they looked fine. When I did a preview of the project, they looked fine. But when I made a video file, those scenes now have black bars at top and bottom. Everything else is in 4:3, as it should be; only clips I used pan&zoom on have been altered. What's going on, and how can I fix it?

Oh -- all my clips and images were 4:3 to start with, and everything was added to the timeline with "keep aspect ratio intact" checked.

Any more information needed?