FULL PRODUCT VERSION :
java version "1.6.0-rc"
Java(TM) SE Runtime Environment (build 1.6.0-rc-b96)
Java HotSpot(TM) Client VM (build 1.6.0-rc-b96, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

A DESCRIPTION OF THE PROBLEM :
I have a JMenuItem with a Icon.
This JMenuItem ist directly added to a JMenuBar.
The Icon is not displayed (just a grey rectangle).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Here is a simple test-file to reproduce the bug.
You only must change the path to the ImageIcon (i can not attach the 
icon, you must use your own ;))

---------- BEGIN SOURCE ----------
import javax.swing.*;


public class JMenuIconBug {


    private static void createAndShowGUI() {
        JFrame frame = new JFrame("TEST");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300,100);
        JMenuItem jmi_TTCLogo = new JMenuItem(new 
ImageIcon("images/1.png")); //$NON-NLS-1$
        jmi_TTCLogo.setHorizontalAlignment(SwingConstants.RIGHT);
        jmi_TTCLogo.setRolloverEnabled(false);
        jmi_TTCLogo.setText("  "); //$NON-NLS-1$
        JMenuBar jmb = new JMenuBar();
        jmb.add(jmi_TTCLogo);
        frame.setJMenuBar(jmb);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

}

---------- END SOURCE ----------
REPRODUCIBILITY :
This bug can be reproduced always.

Release Regression From : 5.0u8
The above release value was the last known release where this 
bug was not reproducible. Since then there has been a regression.