JCombobox does not open it's popup problem....

in the following code :
import java.awt.* ;
import java.awt.event.* ;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;
import java.util.*;
public class CallTiketPnl extends JPanel {
   
    /** Creates a new instance of CallTiketPnl */
    public CallTiketPnl() {
        super();
       
        jTblRes.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null},
                {null, null, null, null}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));  
       
        // These to lines corect the problem but the hightlighting is not corect.
        //jCmbBxIn.setLightWeightPopupEnabled(false);
        jCmbBxIn.setBackground(Color.WHITE);
        jCmbBxIn.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "numero de série", "pin code", "pays", "N° de téléphone" }));
        //jCmbBxIn.setDoubleBuffered(true);


        setLayout(new GridBagLayout());
        setBackground(Color.WHITE);
        gbc.gridx = gbc.gridy = 0;
        add(jLblSearch, gbc);
        gbc.gridx++;        
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.weightx = 1.0;
        add(jTxtFldSearch, gbc);
        gbc.fill = GridBagConstraints.NONE;
        gbc.weightx = 0;
        gbc.gridx++;  
        add(jLblIn, gbc);
        gbc.gridx++;
        add(jCmbBxIn, gbc);      
        gbc.gridx++;
        jBtnSearch.setBackground(Color.WHITE);
        add(jBtnSearch, gbc);

        gbc.gridx = 0;
        gbc.gridy++;
        gbc.gridwidth = 5;
        gbc.fill = java.awt.GridBagConstraints.BOTH;
        gbc.weightx = gbc.weighty = 1.0;
        add(jTblRes, gbc);

        jBtnPrint.setBackground(Color.WHITE);
        gbc.gridwidth = 0;
        gbc.fill = java.awt.GridBagConstraints.NONE;
        gbc.weightx = gbc.weighty = 0;
        gbc.gridx = 4;
        gbc.gridy++;
        add(jBtnPrint, gbc);        
    }
   
    public static void main(String[]args)
    {
        JFrame tstf =new JFrame("test");
        tstf.getRootPane().setLayout(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
       
        gbc.gridx= gbc.gridy = 0;
        gbc.fill = java.awt.GridBagConstraints.BOTH;
        gbc.fill=gbc.BOTH;
        gbc.weightx=gbc.weighty=1;
        tstf.getRootPane().add(new CallTiketPnl(),gbc);
        tstf.pack();
        tstf.show();
        tstf.setDefaultCloseOperation(tstf.EXIT_ON_CLOSE);
    }
   
        GridBagConstraints gbc= new GridBagConstraints();
        JLabel jLblSearch = new JLabel("Search");
        JTextField jTxtFldSearch = new JTextField();
        JLabel jLblIn = new JLabel(" in ");
        JComboBox jCmbBxIn = new JComboBox();
        JTable jTblRes = new JTable();
        JButton jBtnSearch = new JButton("Go");
        JButton jBtnPrint = new JButton("Print");
}




the combo box did not open the popup until the fram is resised to be small.
please help;-)