Error: Unknown command
After invoking AutoCAD, the ArcCAD menu group is loaded, but when an attempt is made to evoke an ArcCAD command, the following error occurs:
AutoCAD always saves the last called menu in the .dwg file. If a file is edited with ArcCAD, the last menu called is ARCAD.MNU, which is saved to the file. If another session is called and the user doesn't want to run ArcCAD, AutoCAD will still load ARCAD.MNU.
Solution or Workaround
Navigate to Tools > AutoCAD menu or Tools > ArcCAD 14 Menu to toggle between menus. Otherwise, type in at the command prompt:
(command "menu" "arcacad")
to get to the AutoCAD Menu or
(command "menu" "arcad14")
to get to the ArcCAD 14 Menu.