The SpacePilot is not supported by Carrara Pro 5.1, as far as I can see. In fact, Carrara is rather unfriendly to the device. The only function that vaguely works is zooming and if you zoom 'past' an object it is difficult or impossible to get the view back. The SpaceNavigator uses the same drivers and I doubt you'll have any better luck with it. I stand to be corrected, but that's my experience so far.