1. Run the terminal command: sudo nautilus
2. Navigate to /etc/grub.d
3. Make sure that in (right mouse click on the file) Properties – Permissions, the Execute (Allow executing file as a program) box is checked for all of the script files so that the scripts will indeed run.
4. Exit from Nautilus (if the system responds with a usershare error, this can be cleared with Ctrl-Z)