Java GUI does not work in Ubuntu

Question

Hello everybody,
I made an GUI application using Swing and Eclipse. When I run it, the GUI shows up, and the program works until I place the pointer on top of the program's window. When I do so, the program freezes and after a couple of seconds I get a message telling me that the program is not responding.
The code itself should not be the problem because I tried several well established Hello Worlds applications. Other users also report that this code works fine on theri computers.
Probably it is important to notice that SWT based Hello World applications work fine on my Ubuntu (only Swing based applications freeze).
It has been suggested that the problem can be in the default JDK used by Ubuntu. I tried to solve the problem in this direction. I typed "aptitude search jdk" in the command line and found out that "sun-java6-jdk" is the only JDK installed on my computer. So, it should be OK.
Any ideas what can be wrong?
The old dicussion about this subject was blocked (it is here: http://forums.sun.com/thread.jspa?threadID=5402905&tstart=0)

Answer 1

// This code generate a text area.
// Taken from http://www.javafaq.nu/java-article743.html
import java.awt.*;
import javax.swing.*;
public class HelloWorldSwing extends JFrame {
         JTextArea m_resultArea = new JTextArea(6, 30);
         //====================================================== constructor
         public HelloWorldSwing() {
             //... Set initial text, scrolling, and border.
             m_resultArea.setText("Enter more text to see scrollbars");
             JScrollPane scrollingArea = new JScrollPane(m_resultArea);
             scrollingArea.setBorder(BorderFactory.createEmptyBorder(10,5,10,5));
             // Get the content pane, set layout, add to center
             Container content = this.getContentPane();
             content.setLayout(new BorderLayout());
            content.add(scrollingArea, BorderLayout.CENTER);
             this.pack();
         public static void createAndViewJFrame() {
             JFrame win = new HelloWorldSwing();
             win.setTitle("TextAreaDemo");
             win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
             win.setVisible(true);
         //============================================================= main
         public static void main(String[] args) {
              SwingUtilities.invokeLater(new Runnable(){
                   public void run(){
                        createAndViewJFrame();
}