Run the testcase below,
you'll see the messageBox and the green trayicon appear
Click on the green trayIcon ->
ava.lang.ClassCastException: java.awt.TrayIcon cannot be cast to java.awt.Component
	at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabber.eventDispatched(BasicPopupMenuUI.java:810)
	at java.awt.Toolkit$SelectiveAWTEventListener.eventDispatched(Toolkit.java:2376)
etc...
comes up
===Test case===
OS: Windows XP
JDK 6,7 
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
public class bug {
 public static void main(String[] args) throws Exception {
 SystemTray tray = SystemTray.getSystemTray();
 TrayIcon ti = new TrayIcon(getImage(), "Hello");
 tray.add(ti);
 
 final JPopupMenu popup = new JPopupMenu("Menu");
 popup.add(new JMenuItem("Item"));
 
 ti.addMouseListener(new MouseAdapter() {
 public void mouseReleased(MouseEvent e) {
 popup.setLocation(e.getX(), e.getY());
 popup.setVisible(true);
 }
 });
 
 JOptionPane.showMessageDialog(null, "message");
 }
 static Image getImage() {
 BufferedImage im = new BufferedImage(32, 35, BufferedImage.TYPE_INT_ARGB);
 Graphics2D g2 = (Graphics2D) im.getGraphics();
 g2.setColor(Color.GREEN);
 g2.fillRect(0, 0, im.getWidth(), im.getHeight());
 g2.dispose();
 return im;
 }
}