Problem in an applet using JTOpen4.0

Hi,
I'm tring to create an applet that using jt400 classes to read an AS400
file.
The com.ibm.as400.access.AS400JDBCDriver() registation is OK!
but the getConnection (Connection connection = DriverManager.getConnection
("jdbc:as400://S655772B/CGIUTI;naming=system;errors=full;libraries=CGIUTI,QGPL;date
format=iso",userString,passwordString);) return null Exception and doesn't
read the file (there are no errors in JVM consolle!)

Here's the code :
//***********************************************************
import java.lang.Object.*;
import java.net.URLConnection.*;
import java.net.URL.*;
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import com.ibm.as400.access.*;
import java.sql.*;

public class AccessoDB extends Applet implements ActionListener
{

   Label systemPrompt;
   Label userPrompt;
   Label passwordPrompt;
   TextField systemField;
   TextField userField;
   TextField passwordField;
   Button okButton;
   Button cancelButton;
   String systemString;
   String userString;
   String passwordString;
   String commandString;

   public void init()
   {


      setLayout(new FlowLayout());      
      systemPrompt = new Label("Nome Sistema AS400 ");
      add(systemPrompt);
      systemField = new TextField(15);
      add(systemField);
      userPrompt = new Label("Utente");
      add(userPrompt);
      userField = new TextField(10);
      add(userField);
      passwordPrompt = new Label("Password");
      add(passwordPrompt);
      passwordField = new TextField(10);
      add(passwordField);
      okButton = new Button("OK");
      okButton.addActionListener(this);
      add(okButton);
      cancelButton = new Button("Cancel");
      cancelButton.addActionListener(this);
      add(cancelButton);
   }

   public void paint(Graphics g)
   {
        
      if ((systemString != null) &&
          (userString != null) &&
          (passwordString != null))

      {
         g.drawString("Sistema:" + systemString, 60, 100);
         g.drawString("Utente:" + userString, 60, 120);
         g.drawString("Connessione a Host ...", 60, 160);
         g.drawString("Connessione a CGIUTI ...", 60, 180);
         String system=systemString;
         try
         {

           // Load the IBM Toolbox for Java JDBC driver.
            DriverManager.registerDriver(new 
com.ibm.as400.access.AS400JDBCDriver());
                   g.drawString("Driver OK!.", 60, 200);
            Connection connection = DriverManager.getConnection 
("jdbc:as400://S655772B/CGIUTI;naming=system;errors=full;libraries=CGIUTI,QGPL;date
format=iso",userString,passwordString);
            g.drawString("Connessione OK!.", 60, 220);
            DatabaseMetaData dmd = connection.getMetaData ();
            Statement select = connection.createStatement ();
            ResultSet rs = select.executeQuery ("SELECT * FROM CGIUTI" 
+ dmd.getCatalogSeparator() + "WLUTE00F");
            g.drawString("Connessione Query!.", 60, 240);
            ResultSetMetaData rsmd = rs.getMetaData ();
            int columnCount = rsmd.getColumnCount ();
            StringBuffer dashedLine;
           while (rs.next ()) {
                for (int i = 1; i <= columnCount; ++i) {
                    String value = rs.getString (i);
                    if (rs.wasNull ())
                        value = "<null>";
                         g.drawString(value, 60, 260);
                }
            }


          connection.close();



         }
         catch (Exception e)
         {
            g.drawString("Connessione Fallita."+ e.getMessage(), 60, 220);

         }

      }

   }

   public void actionPerformed(ActionEvent e)
   {
      if (e.getActionCommand() == "Cancel")
      {
           System.exit(0);
      }

      systemString = systemField.getText();
      userString = userField.getText();
      passwordString = passwordField.getText();
      repaint();

   }

}

// end of Code ****************************************************

P.S.:In the same jar file are saved all jt400 classes needed!

Thanks in advance!!

Vincenzo Amoruso
System Project s.r.l.
Andria(BA) - Italy