There, I've done and made an SSCCE illustrating my problem:

<SSCCE>

package bug;

/*A rather simple example of setMediaTime() using a SeekBar slider
* More advanced functionality such as updating the seek bar is omitted.
* Note that you also have to resize the frame for the Player  to become
* visible initially.
*/

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.media.Time;
import javax.media.bean.playerbean.*;

public class Frame1 extends JFrame {
  private final String mediaFile = "C:\\cow[1].mpg";
  //Tested on several different mpeg and avi files, so this can't be
the problem.
  //Change mediaFile to any mpeg or avi of supported format on your
computer.

  JPanel contentPane;
  BorderLayout borderLayout1 = new BorderLayout();
  MediaPlayer thePlayer = new MediaPlayer();
  JSlider theSeekBar = new JSlider();

  //Construct the frame
  public Frame1() {
    enableEvents(AWTEvent.WINDOW_EVENT_MASK);
    try {
      init();
      this.pack();
      this.setSize(500,350);
      this.setVisible(true);
      thePlayer.repaint(); //This doesn't work
      this.repaint();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }

  //Component initialization (Create an instance of Player and a simple
Seek bar)
  private void init() throws Exception  {
    contentPane = (JPanel) this.getContentPane();
    contentPane.setLayout(borderLayout1);
    this.setTitle("JMF Repaint Bug demo");
    theSeekBar.setMinimum(0);
    theSeekBar.setMaximum(100);
    thePlayer.setMediaLocation("file:"+mediaFile);
    thePlayer.realize();
    thePlayer.prefetch();
    theSeekBar.setValue(0);
    theSeekBar.addChangeListener(new SeekBarListener(thePlayer));
    contentPane.add(thePlayer,  BorderLayout.NORTH);
    contentPane.add(theSeekBar,  BorderLayout.SOUTH);
  }

  protected void processWindowEvent(WindowEvent e) {
    super.processWindowEvent(e);
    if (e.getID() == WindowEvent.WINDOW_CLOSING) {
      System.exit(0);
    }
  }
}
class SeekBarListener implements ChangeListener {
  private javax.media.bean.playerbean.MediaPlayer target;

  public SeekBarListener(javax.media.bean.playerbean.MediaPlayer targ){
    this.target = targ;
  }

  public void stateChanged(ChangeEvent e) {

        JSlider source = (JSlider) e.getSource();
        if (!source.getValueIsAdjusting()) {
          long durationNanoseconds =
(this.target.getDuration().getNanoseconds());
          int percent = source.getValue();
          long t = (durationNanoseconds / 100) * percent;
          Time newTime = new Time(t);
          this.target.stop();
          this.target.setMediaTime(newTime);
          //So far, so good...
          //The Seek bar knob on the Plyers default control panel even
moves, but:
          this.target.repaint(); //does not work
          this.target.getVisualComponent().repaint(); //does not work
either
          //Result: The players visual component still displays the old
frame
        }
      }
    }

</SSCCE>

Could you guys please run this example and see if it performs the same
way as described in my previous post on your system?
(And, most importantly, why? And how to correct this?)