According to SQE, the problem described in 6458497 still reproducible with jdk 7.0 b07
(however I was unable to reproduce it :( Here is a test which was used to reproduce the
problem.

import java.awt.*;
import javax.swing.*;

public class AltTab {
  public static void main(String[] args) {
    try {
        UIManager.setLookAndFeel(UIManager
             .getSystemLookAndFeelClassName());
    } catch(Exception e) {
    }
    JFrame frame = new JFrame("Alt-Tab Frame");
    JMenuBar menuBar = new JMenuBar();
    frame.setJMenuBar(menuBar);
    JMenu fileMenu = new JMenu("File");
    char fileMenuMnemonic = 'F';
    fileMenu.setMnemonic(fileMenuMnemonic);
    menuBar.add(fileMenu);
    frame.setSize(100,100);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);
  }
}