Recently Space Navigator updated their drivers from 1.6.2 to 1.6.3.
I updated my drivers on my Macbook pro with system 10.6 and the new drivers switched the up-down and front-back motion of my avatar when controlled by the space navigator!
I went to the driver download page on the space navigator download site and reloaded the historic 1.6.2 drivers and all was restored!
You could also go to the preferences page in viewer 2 and re-assign the space navigator mapping to the SL motion mapping. Go to Move and view >Other devices>
find the boxes x-axis mapping, y-axis mapping and z-axis mapping numbered 0,1,2
renumber them until you get the correct relationship between the space navigator and the motion of your avatar or camera!
I love my space navigator for moving my avatar and camera with my left hand while I mouse with my right!
Two handed motion rules!
Except when I fight in tournaments then I use a game controller!
Patio.