As far as I can see,
I ditched the .mnu file forever, I have the .mns, I menuload the .mns, all users load the .mnc file.
Whenever I change the .mns file, the users see the changes next time they open AutoCAD, it seems to work real well.
If you have multiple versions of AutoCAD, you place a copy od the updated .mns file in a seperate directory (folder) ie ACAD_2002, ACAD_2005 etc.
If you are replacing the old menu, then overwrite the mns and delete the mnr and mnc, they will be re compiled after you menuload or open AutoCAD back up.
Sound Good?