IDE (Netbeans, Eclipse, JDeveloper) Debugger hangs process on Linux

Given the java class below, debug that source code with Netbeans (I used 6.1), Eclipse or JDeveloper on Linux using JDK 6 update 7 (it works fine with jdk 1.5.0) and put a breakpoint on the line i++, debug the source file and cause the debugger to trigger the breakpoint. Note the entire Linux (I use GNome) Window manager is frozen, both keyboard and mouse don't respond anymore.

package client;

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

public class Frame1 extends JFrame implements ItemListener {
  private JComboBox jComboBox1 = new JComboBox(new String[] { "Apples", "Oranges", "Mangoes"});

  public Frame1() {
    try {
      jbInit();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  private void jbInit() throws Exception {
    this.getContentPane().setLayout( null );
    this.setSize( new Dimension(400, 300) );
    jComboBox1.setBounds(new Rectangle(45, 25, 235, 25));
    jComboBox1.addItemListener(this);
    this.getContentPane().add(jComboBox1, null);
    this.setVisible(true);
  }

  public void itemStateChanged(ItemEvent e) {
    System.out.println("Entering ItemStateChanged");
    int x = 1;
    x++; // put a breakpoint on that line and it will freeze
    System.out.println("Exiting ItemStateChanged");
  }
  public static void main(String[] s) {
    new Frame1();
  }
}