Pressing ALT obscures components when using Windows L&F

I have a JFrame that displays a big JLabel in the background and a
JCheckBox in the front.

When using the Windows L&F and I press the Alt-key the JLabel is
repainted but not the JCheckBox in front of it. As a consequence the
checkbox disappears. Forcing a repaint (e.g. by resizing the frame)
will make the checkbox re-appear.

When not using the Window L&F everything is fine.

Any suggestion how to work around this problem?

ub

Here the sourcecode:
-----
import java.awt.Color;

import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.UnsupportedLookAndFeelException;

public class AltKeyRepaint {
    public static void main(String args[]) throws ClassNotFoundException,
            InstantiationException, IllegalAccessException,
            UnsupportedLookAndFeelException {
        // Use the System (i.e. "Windows") L&F
        javax.swing.UIManager.setLookAndFeel(javax.swing.UIManager
                .getSystemLookAndFeelClassName());

        // The frame to display the sample
        JFrame frame = new JFrame("Frame");
        frame.setSize(250, 200);
        frame.getContentPane().setLayout(null);

        // A big colored label in the background
        JLabel label = new JLabel("A sample label in the background");
        label.setBackground(Color.ORANGE);
        label.setOpaque(true);
        label.setBounds(5, 5, 200, 150);

        // A check box on top of the background label
        JCheckBox chkBox = new JCheckBox("a check box on top");
        chkBox.setBounds(30, 30, 150, 20);

        // Add the label and check box to the frame
        frame.getContentPane().add(chkBox);
        frame.getContentPane().add(label);

        // display it
        frame.show();

        // Now pressing the ALT key will repaint the label, but not the
        // check box, i.e. the check box disappears.
        // Forcing a repaint (e.g. by resizing the frame) will make the
check
        // box re-appear.

        // Without the Windows L&F (first statement of function) everything
        // will be fine.
    }
}