FULL PRODUCT VERSION :
java version "1.7.0-ea-fastdebug"
Java(TM) SE Runtime Environment (build 1.7.0-ea-fastdebug-b135)
Java HotSpot(TM) Client VM (build 21.0-b05-fastdebug, mixed mode)

A DESCRIPTION OF THE PROBLEM :
JTabbedPane is worse.

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6747580

Tabs aren't renderd.

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

public class Editor {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
                } catch (Exception e) {
                }
                JFrame frame = new JFrame("Editor");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new GridLayout(3, 1));
                JTabbedPane tabbedPane = new JTabbedPane();
                tabbedPane.addTab("00001", new JScrollPane(new JTextArea()));
                tabbedPane.addTab("00002", new JScrollPane(new JTextArea()));
                frame.add(tabbedPane);
                tabbedPane = new JTabbedPane(JTabbedPane.TOP, JTabbedPane.SCROLL_TAB_LAYOUT);
                tabbedPane.addTab("00001", new JScrollPane(new JTextArea()));
                tabbedPane.addTab("00002", new JScrollPane(new JTextArea()));
                frame.add(tabbedPane);
                tabbedPane = new JTabbedPane(JTabbedPane.BOTTOM, JTabbedPane.SCROLL_TAB_LAYOUT);
                tabbedPane.addTab("00001", new JScrollPane(new JTextArea()));
                tabbedPane.addTab("00002", new JScrollPane(new JTextArea()));
                frame.add(tabbedPane);
                frame.setSize(100, 300);
                frame.setVisible(true);
            }
        });
    }
}


REPRODUCIBILITY :
This bug can be reproduced always.