Hi Shatarpi -
Yes, the MEL prompt is correct . The 3DMouse News window indicates the add-in is installed - permissions may be keeping it from being available.
If Maya is installed as administrator, the 3Dconnexion software requires the same privileges. To add administrator privileges:
1. Stop the driver [Start --> All Programs --> 3Dconnexion --> Driver --> Stop Driver] and close Maya.
2. Locate 3dxsrv.exe and add the permission. C:\Program Files\3Dconnexion\3Dconnexion 3DxSoftware\3DxWare\3dxsrv.exe
Right click on 3dxsrv.exe --> Choose Properties --> select the Compatibility tab --> select only 'Run as administrator'
3. Start the driver [Start --> All Programs --> 3Dconnexion --> Driver --> Start Driver]
4. Restart Maya
The 3DxMaya add-in depends on the command MagellanStartup being executed by the usersetup.mel - this is why using MagellanStartup at the MEL prompt works. Maya will only load the first usersetup.mel it finds. When another script or add-in such as Maya's Bonus Tools or GoZ is installed, they add their own usersetup.mel files.
You should find the usersetup.mel in Maya's ..\scripts\startup folder.