Menu editor not working

[Thomas Blasejewicz]

Good morning everyone.
I am trying to use Mint 19, but since this seems to be based on Ubuntu, 
someone suggested I may not be thrown out of here right away.

Problem:
I made (as far as I can tell identical) clean new installations of Mint 
19 (formerly used Mint 17.2) on 3 different PCs, all o which are 
somewhat older.
The menu editor does work in 2 out of them, including one very old PC, 
but not the one here in my office.

When I try to add some "New Item", there is no response to clicking that 
button at all.
Other buttons like "Properties" do not work.
When asked whether I would like to add a launcher created on the desktop 
also to the menu, this does not work either.
I also installed Alacarte, but the behavior is exactly the same.

Is there a magic trick, some setting anywhere, that can resolve this 
"problem"?
It is not really a problem, but used to work under Mint 17.

Thank you.
Thomas