No such element exception when applet window closed

Question

My applet can throw a NoSuchElementException as it closes during sudden death. The Java Console reports:
Exception in thread "AWT-EventQueue-2" java.util.NoSuchElementException
     at java.util.LinkedList.getFirst(Unknown Source)
     at java.awt.SequencedEvent.getFirst(Unknown Source)
     at java.awt.SequencedEvent.dispatch(Unknown Source)
     at java.awt.EventQueue.dispatchEvent(Unknown Source)
     at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
     at java.awt.EventDispatchThread.run(Unknown Source)Sometimes that sequence displays once, sometimes twice. The error appears to be 90% or more repeatable.
1) open link in new window http://r0k.us/graphics/SIHwheel.html
2) view Color Log (menu item Help -=> Show Log)
3) close the whole browser window
It does not appear to happen without the dialog for the Color Log displayed. Nor does it appear to happen simply upon leaving that page. I'm guessing it is some sort of race condition as the applet is shut down and it doesn't have the surrounding window it started with. It only happens when running as an applet. When ran as a program, it always shuts down cleanly.
It occurs less often if you:
1) open the link in new window
2) leave the page
) come back to it while the Java Console is still alive (before JVM goes away)
3) view the Color Log
4) close the browser window.
I am running 64-bit Windows 7, and have observed this problem in Firefox, IE, and Chrome.
With no hints as to where within my code this is occurring (if indeed it is within "my" code), I have no idea how to write an SSCCE. The exception seems to relate to enumerations, which I believe must be occuring during the shut down seqence. See:
* http://download.oracle.com/javase/1.5.0/docs/api/java/util/NoSuchElementException.html
What can I try doing to prevent the error from occurring? (Besides not closing the browser window while my applet is running and has a dialog open. ;) )
*(added immediately before posting)* I just noticed that if any of the first three dialogs in the Help Menu are open, this behavior can occur. So it probably has nothing to do with the tables in the Color Log. The fourth, About, item is a simpler modal dialog, and you aren't even able to close the browser window while it is open.
Now that I know the crash can happen with any of the non-modal dialogs, I will write an SSCCE, just to see if it occurs in a much simpler applet, if nothing else.

Answer 1

As promised, an SSCCE with build instructions and an applet environment.
CloseMyWindow.java import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.IOException;
import java.net.URL;
import javax.swing.*;
public class CloseMyWindow  extends JApplet
    public JPanel makeContent() {
     JButton help = new JButton("Help");
     help.addActionListener( new ActionListener() {
         public void actionPerformed(ActionEvent e) {
          Dimension size = new Dimension(400, 250);
          HelpBox hb = new HelpBox("CloseMyWindow Help",
              "cmwHelp.html", false, size);
     JPanel jp = new JPanel();
     jp.add(help);
     return jp;
    // method expected by applets
    public void init()
     try {
         javax.swing.SwingUtilities.invokeAndWait(new Runnable() {
          public void run() {
              JPanel frame = makeContent();
              setContentPane(frame);
     } catch (Exception e) {
         System.err.println("makeContent() failed to complete: " + e);
         e.printStackTrace();
    public static void main(String[] args)
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                frame.add(new CloseMyWindow().makeContent());
                frame.pack();
                frame.setVisible(true);
class HelpBox extends JDialog
{   // general window for display of HTML page
    HelpBox(String title, String pUrlS, boolean modal, Dimension pSize)
     super((Frame)null, title, modal);
     final String     urlS  = pUrlS;
     final Dimension     size  = pSize;
     SwingUtilities.invokeLater(new Runnable() {
         public void run() {
          setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
          JEditorPane ep = new JEditorPane();
          ep.setEditable(false);
          try {
              URL url = getClass().getResource(urlS);
              ep.setPage(url);
              JScrollPane eps = new JScrollPane(ep);
              eps.setPreferredSize(size);
              getContentPane().add(eps, BorderLayout.CENTER);
          } catch (IOException ioE) {
              System.err.println("Unable to display help pane");
              ioE.printStackTrace();
          pack();
          setLocationRelativeTo(null);
          setVisible(true);
}cmwManifest.txt (be sure to end line with a carriage return) Main-Class: CloseMyWindowcmwHelp.html <html>
<head><title>Help for CloseMyWindow</title></head>
<body>
Good, you've opened this dialog.  Now close the browser window containing
my applet.
</applet>
</body>
</html>cmw.html <html>
<head><title>Close My Window</title></head>
<body>
<applet code="CloseMyWindow.class"
        archive="CloseMyWindow.jar"
        width="450" height="300">
Your browser is completely ignoring the <i>applet</i> tag!
</applet>
</body>
</html>1) capture the 4 code segments above and save them as correspondingly-named files.
2) compile:
] javac CloseMyWindow.java
3) build the jar:
] jar cvfm CloseMyWindow.jar cmwManifest.txt *.class cmwHelp.html
4) test the jar:
] java -jar CloseMyWindow.jar
5) run the applet. Open page cmw.html in a new browser window
6) enable Java Console (mine is set to autostart on any applet or JNLP)
7) click the applet's Help button. A new dialog should open up.
8) close the browser window
9) observe if an error is reported in Java Console
I am seeing the error in this small applet. Maybe the .java file will give you guys some clues.