FULL PRODUCT VERSION :
Version 1.5.0_05 or higher

EXTRA RELEVANT SYSTEM CONFIGURATION :
Appears only when a Synth Look and Feel is set.

A DESCRIPTION OF THE PROBLEM :
By using a Synth Look and Feel and an _empty_ JTextPane no caret will be displayed. This occurs only with JVM 1.5.0_05 or higher including Mustang. With JVM 1.5.0_04 the problem doesn't occur.


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.io.ByteArrayInputStream;
import java.io.InputStream;

import javax.swing.JFrame;
import javax.swing.JTextPane;
import javax.swing.UIManager;
import javax.swing.plaf.synth.SynthContext;
import javax.swing.plaf.synth.SynthLookAndFeel;
import javax.swing.plaf.synth.SynthPainter;

public class TextPaneTest extends JFrame
{
  private static String synthXml = "<synth>" +
  "    <style id=\"all\">" +
  "      <object id=\"customPainter\" class=\"TextPaneTest$TextPanePainter\" />" +
  "      <font name=\"Verdana\" size=\"12\"/>" +
  "    </style>" +
  "    <bind style=\"all\" type=\"REGION\" key=\".*\"/>" +
  "    <style id=\"textPane\">" +
  "      <state>" +
  "        <color value=\"#FFFFFF\" type=\"BACKGROUND\"/>" +
  "        <painter method=\"textPaneBackground\" idref=\"customPainter\" />" +
  "      </state>" +
  "    </style>" +
  "    <bind style=\"textPane\" type=\"region\" key=\"TextPane\"/>" + 
  "</synth>";
 
  public static void main(String[] args) throws Exception
  {
    InputStream is = new ByteArrayInputStream(synthXml.getBytes("UTF8"));
    SynthLookAndFeel laf = new SynthLookAndFeel();
    laf.load(is, TextPaneTest.class);
    UIManager.setLookAndFeel(laf);   
    new TextPaneTest();   
  }

  public TextPaneTest()
  {
    JTextPane textPane = new JTextPane();
    textPane.setText("Delete this text - caret disappers!");
    add(textPane);

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(new Dimension(400, 300));
    setLocationRelativeTo(null);
    setVisible(true); 
  }

  public static class TextPanePainter extends SynthPainter
  {
    public void paintTextPaneBackground(SynthContext sc, Graphics g, int 
x, int y, int w, int h)
    {
      //Also changes the caret color for empty textPanes with Java 1.5.0_05 or later!
      g.setColor(Color.YELLOW);
      g.fillRect(x, y, w, h);
    }
  }
   
} 

---------- END SOURCE ----------

Release Regression From : 5.0u4
The above release value was the last known release where this 
bug was known to work. Since then there has been a regression.