FULL PRODUCT VERSION :
java version "1.5.0_11"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_11-b03)
Java HotSpot(TM) Client VM (build 1.5.0_11-b03, mixed mode)
1.6.0_02

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

A DESCRIPTION OF THE PROBLEM :
JFrame windows that have setUndecorated(true) cannot be tiled from the
Windows task bar.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
  To reproduce:

   1) Start multiple windows with setUndecorated(true) that get grouped into a
        single menu item on the Windows task bar.
   2) Right-click the menu item.
   3) Click Tile Horizontally or Tile Vertically.
   4) Notice that nothing happens.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Windows should be tiled.
ACTUAL -
Windows did not move or resize. Nothing happened.

REPRODUCIBILITY :
This bug can be reproduced always.

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

public class Bug extends JFrame {

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

  private Bug() {
    super("Bug");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    getContentPane().add(
      new JLabel("You cannot tile this."),
      BorderLayout.CENTER
    );
    setUndecorated(true);
    getRootPane().setWindowDecorationStyle(JRootPane.FRAME);
    pack();
    setVisible(true);
  }
}
---------- END SOURCE ----------