I have solved this issue on ARCHLINUX creating an symlink:
sudo ln -s /usr/lib/networkmanager/nm-vpnc-auth-dialog /usr/lib/gnome-shell/nm-vpnc-auth-dialog
I have solved this issue on ARCHLINUX creating an symlink:
sudo ln -s /usr/lib/ networkmanager/ nm-vpnc- auth-dialog /usr/lib/ gnome-shell/ nm-vpnc- auth-dialog