I have a similar issue with a SpaceNavigator and Inventor 2012 Ultimate. Almost completely no motion, untill I click on Google Chrome, then I can see the Inventor model fly around silky smooth. Click back to focus on Inventor, and nothing moves.
I did look up I/O in task manager, there seem to be quite a few things consuming read & write I/O when I move the SpaceNavigator, yes one of the biggest is Google Chrome web browser.
I tried fully turning off the AVG (free basic) antivirus and I added the exception to windows firewall for the 3DX server as I saw in another forum.
I have the latest driver downloaded from 3D connexion.
Freshly installed 64b Windows 7 (home premium) on a new Crucial 128GB SSD. Asus M2N-SLI Deluxe MB, 4 GB Ram, AMD 9500 Quad Core. Video is an Nvidia 8800 GTS.
(This is my home based home made CAD station to work from home as apposed to my lenovo system and SpacePilot Pro in the office. I've been Running 3dX devices since spaceballs had serial connections.
I can try my SpacePilot Pro tonight just to see what happens, but I believe that is a different driver set.
Do you Guys have any other suggestions?