No, no extra key frames. Believe me, I checked. The scene above was made from scratch as a test after it appeared in another file I was working on. I then made ANOTHER file from scratch using Carrara plants on a terrain. All the replicated objects get this wormhole/warp drive trail on them when I turn on vector-based motion blur, even though they don't move. I guess it must be a bug, but if anyone has time to set up a basic scene with a terrain and surface replicated objects, I'd be interested in hearing how it renders with vector-based motion blur clicked.

SF to LA: From June 1 to June 7 2007 I will be riding my bicycle 545 miles to help support people living with HIV/AIDS. Please visit my homepage: http://www.aidslifecycle.org/6010