A bug? Maybe not. Try 3D motion blur instead. Also, why are you rendering using created PERSPECTIVE cameras? My suggestion would be to create an actual camera, not a default Maya viewable camera (persp, side, front, top).
Another thing that usually works when I have rendering issues is to create a whole new scene, import the old scene into it, create a new camera and render. Can't explain why that works, but it does every time.
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida