HSeparator doesn't show

[jody <jody xha gmail com>]

Hi

I want to make a dialog which has inputs for two different entities,
where the two input areas are separated by a line.

In my Gtk::Dialog's constructor i do:

    Gtk::HSeparator hsep;
    m_VBox1.pack_start(m_HBox1,  Gtk::PACK_SHRINK);
    m_VBox1.pack_start(hsep, Gtk::PACK_EXPAND_WIDGET);
    m_VBox1.pack_start(m_HBox2, Gtk::PACK_SHRINK);

    get_vbox()->add(m_VBox1);

    show_all_children();


When the dialog is displayed, the contents of the two HBoxes are
visible, but the separator is not.
I have tried to pack the separator with Gtk:PACK_SHRINK, too, to no avail.
The same holds for VSeparator.
I also tried both settings for set_has_separator (bool setting).

Is there anything special to do in order to make a Separator visible
inside a dialog?

Thank You
  Jody