I've had to reinstall the space navigator driver a number of times.. every time I even update my ati video drivers, the space navigator craps out. (I can tell when it's lights don;t come on after boot.)

Also the latest ati drivers did NOT kill the SN this last time.

I'd just reinstall the spacemouse driver after installing poser pro, and see if that resolves the issues between them.

Way too many people take way too many things way too seriously.