Thanks Alfred and renderlens, I had the same result.
Uninstalled 3dconnexion driver and the scene manager works; reinstalled their latest driver and it stopped working.
3DxStudio.ms script auto-runs on session start up from C:\ProgramData\Autodesk\ApplicationPlugins\3DxStudio.bundle\Contents\scripts. Deleting or moving it means it doesn't run on start up, the scene state manager works(!) and the 3Dconnexion mouse doesn't work.
I tried moving it to C:\Program Files\Autodesk\3ds Max 2017\scripts\Startup but same thing happens.
The workaround for me was to move the script to the C:\Program Files\Autodesk\3ds Max 2017\scripts folder so it DOESN'T auto run, but is easy to run manually from the default script folder after session start up.
The 3d mouse and the scene state manager both now work for me! Simultaneously!! I'll probably see about making a custom button so it's just one click, until such time as the bug is fixed by whoever it belongs to.
Thanks for all your help Alfred!