First, uninstall all CDG Purge files and delete all directories (C:\Program Files\CDG...)
Second, install CDG 3.0
Next, copy the following files in to a temporary directory (so to save a copy of them)
AcadInst.exe
AcadInst.ini
AcadInst.log
Next, delete all 3.0 files (including the mapping in AutoCAD), except for the three files in a different directory mentioned above.
Next, install 4.0
Next, move copied files to the 4.0 directory location.
Finally, remap AutoCAD to the latest CDG directory.
If you still can't get it to work, then keep trying. It took me several tries to figure it all out.