I'd tried (PCman) a different file manager, without changing anything in
Nautilus.
Suddenly it took priority on my Ubuntu shortcut menu. So I uninstalled it.
But now my shortcut menu doesn't work anymore for opening directories.
Example for my /home directory I get an error window saying something like
"Impossible opening the place « file:///home/jean »"
and another line beneath "No application is register to manage that file"

(I understand the URI target is considered as a file instead of a directory)

And, at the opposite side, for all the file targets it works...

Any idea please ?