Hi torsten, for some reason newer 3DConnexion drivers on the Mac stopped working with MoI, I don't know why and they have been unresponsive when asked about it. I should be able to investigate it for MoI v4 but for now if you install an older driver version it should work, see here for which version:
http://moi3d.com/forum/index.php?webtag=MOI&msg=7986.1

- Michael