I think that the 3dconnexion driver website may be temporarily serving out blank files, as I've tried to install the win7 x64 drivers for the Space Navigator on several computers, only to find that the installer doesn't exactly work..
Could someone verify that it's a blank file from their download side? The file downloads I get for either of the Win7 x86 or x64 editions are consistently less than 1 kb..
Simply go to http://www.3dconnexion.com/service/drivers.html Select Space Navigator. Win x64 or x32. Double click, and you'd get the incompatibility error.
Update - 3ds download site was down that weekend. They've since put it back up.