GlassPane not visible over JDialog

I'm trying to see the GlassPane over JDialog but I got nothing visible over it. W开发者_StackOverflowhy does it happen? How can I make the GlassPane visible over the JDialog?

Here's what I'm doing:

public class New_Window extends JDialog {

    public New_Window(int Screen_Index, int Start_Panel, int Length) {
        super(new Frame(Monitors.getInstance().getNextDevice()
                .getDefaultConfiguration()), Title, false);
        setLayout(new BorderLayout());
        setGlassPane(glassPane);
        getGlassPane().setVisible(true);
        getContentPane().setBackground(Color.black);
        JPanel Container = new JPanel(new FlowLayout(FlowLayout.CENTER, 2, 2));
        Container.setOpaque(false);
        getContentPane().add(Container, BorderLayout.CENTER);
        [...]
    }

}

Note: I'm using Java version 6 update 24. I'm using a custom GlassPane with its opaque value set to false.

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Read the section from the Swing tutorial on Using a Glass Pane for a working example. Start with the example code and remove code you don't need.