FULL PRODUCT VERSION :
1.6.0_13-b03 (Windows test case)
1.6.0_13-b03 (Linux test case)

ADDITIONAL OS VERSION INFORMATION :
Linux xxxxxxx 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:58:03 UTC 2009 x86_64 GNU/Linux
Microsoft Windows Server 2003 Service Pack 2

A DESCRIPTION OF THE PROBLEM :
When running under the Nimbus look and feel, JProgressBar paints the orange progress bar a couple of pixels outside/to the left of its painted background, for progress values <= 6.

The problem is reproducible on both Linux (Ubuntu 9.04, Java 6 update 13) and Windows (Server 2003 Java 6 update 13).

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
The attached test case reproduces the problem always. Increment the JSpinner and see that the progress bar displays the glitch when value <= 6.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The progress bar should be painted inside its background for all values.
ACTUAL -
The progress bar is pained outside its background for values <= 6.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
    public static void main(String[] args) throws Exception {
        SwingUtilities.invokeAndWait(new Runnable() {
            public void run() {
                try {
                    UIManager.setLookAndFeel("com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
                    JFrame frame = new JFrame("JProgressBar Nimbus TestCase");
                    frame.setLayout(new FlowLayout());
                    final JProgressBar bar = new JProgressBar();
                    final JSpinner spinner = new JSpinner(new SpinnerNumberModel(0, 0, 100, 1));
                    spinner.addChangeListener(new ChangeListener() {
                        public void stateChanged(ChangeEvent e) {
                            bar.setValue((Integer)spinner.getValue());
                        }
                    });
                    frame.add(bar);
                    frame.add(spinner);
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
                }
                catch (Exception e) {
                    throw new RuntimeException(e);
                }
            }
        });
    }
---------- END SOURCE ----------