JMenuBar display quirks with some window managers on Linux with Java 6

Question

When I run this code on Windows with Java 5 or Java 6, it works fine.
When on Linux with Java 5, it works fine.
When on Linux with Java 6 in KDE, it works fine.
When on Linux with Java 6 with twm or e17, the JMenu shows when I click on the JMenuBar, but goes away as soon as I release the mouse button. If I manually move or resize the window, it then works fine.
If I remove setLocationByPlatform(true), the menu bar works, but it does not position the window by platform, which is the desired behavior.
Am I doing something wrong, is there something wrong with both twm and e17, or is this a bug?
import java.awt.Dimension;
import java.awt.Label;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JMenuBar;
import javax.swing.JMenu;
import javax.swing.JMenuItem;
import javax.swing.WindowConstants;
public class Test extends JFrame {
    public Test() {
        super();
        setDefaultCloseOperation( WindowConstants.EXIT_ON_CLOSE );
        getContentPane().add( new Label( "Hello World" ) );
        JMenuBar mainMenu = new JMenuBar();
        setJMenuBar( mainMenu );
        JMenu helpMenu = new JMenu();
        mainMenu.add( helpMenu );
        helpMenu.setMnemonic( 'H' );
        helpMenu.setText( "Help" );
        JMenuItem help_about = new JMenuItem();
        helpMenu.add( help_about );
        help_about.setMnemonic( 'A' );
        help_about.setText( "About" );
        help_about.addActionListener(
            new ActionListener() {
                public void actionPerformed( ActionEvent evt ) {
                    System.out.println( "HELP!" );
        pack();
        setLocationByPlatform( true );
        setVisible( true );
    public static void main( String[] args )
        throws Exception {
        java.awt.EventQueue.invokeLater(
            new Runnable() {
                public void run() {
                    Test test = new Test();
}

Answer 1

In 10.1.3, there's an option to disable the splash screen on the Environment Page in preferences (although, of course, it's not much use if you never get to the main window because of the dialog popping up behind the splash screen... :) )
The bug with the dialog appearing behind the splashscreen is fixed in the upcoming 11g release. FWIW, it's a problem that appears to be unique to X-based systems, where for some reason the splashscreen window ends up with some super-ueber topmost property that forces all other windows to go behind it.
There's also a command line flag to suppress the splashscreen in 11g.
Thanks,
Brian