FULL PRODUCT VERSION :
java version "1.5.0_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_05-b05)
Java HotSpot(TM) Client VM (build 1.5.0_05-b05, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Windows XP Home SP2

EXTRA RELEVANT SYSTEM CONFIGURATION :
Our customer uses some (unknown to me) Windows XP-Style/Theme!

A DESCRIPTION OF THE PROBLEM :
Within our application (running on our customers machines) we get the following exception:

java.lang.NullPointerException
	at java.awt.Dimension.<init>(Dimension.java:91)
	at javax.swing.plaf.basic.BasicProgressBarUI.getPreferredSize(BasicProgressBarUI.java:757)
	at javax.swing.JComponent.getPreferredSize(JComponent.java:1582)
	at java.awt.GridBagLayout.GetLayoutInfo(GridBagLayout.java:911)
	at java.awt.GridBagLayout.getLayoutInfo(GridBagLayout.java:816)
	at java.awt.GridBagLayout.ArrangeGrid(GridBagLayout.java:1412)
	at java.awt.GridBagLayout.arrangeGrid(GridBagLayout.java:1372)
	at java.awt.GridBagLayout.layoutContainer(GridBagLayout.java:712)
	at java.awt.Container.layout(Container.java:1401)
	at java.awt.Container.doLayout(Container.java:1390)
	at java.awt.Container.validateTree(Container.java:1473)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validate(Container.java:1448)
	at java.awt.Window.show(Window.java:507)
	at java.awt.Component.show(Component.java:1300)
	at java.awt.Component.setVisible(Component.java:1253)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Since the problem only arises on our customers side where we do only have a very limited access, I think the cause of the problem is as follows.
- Windows Look&Feel (com.sun.java.swing.plaf.windows.WindowsLookAndFeel)

- XPStyle returns ����null����:
   /** Get a named <code>Dimension</code> value from the current style
     *
     * @param key a <code>String</code>
     * @return a <code>Dimension</code> or null if key is not found
     *    in the current style
     */
    synchronized Dimension getDimension(String key) {
	Dimension d = (Dimension)map.get("Dimension "+key);
// assume d==null
	if (d == null) {
	    String str = getString(key);
// assume str==null, skip if
	    if (str != null) {
		StringTokenizer tok = new StringTokenizer(str, " \t,");
		d = new Dimension(parseInt(tok.nextToken(), 0),
				  parseInt(tok.nextToken(), 0));
		map.put("Dimension "+key, d);
	    }
	}
// return null
	return d;
    }


- then WindowsProgressBarUI returns ����null����
    protected Dimension getPreferredInnerHorizontal() {
	XPStyle xp = XPStyle.getXP();
	if (xp != null) {
// return null
	    return xp.getDimension("progress.bar.normalsize");
	} else {
	    return super.getPreferredInnerHorizontal();
	}
    }

- then BasicProgressBarUI feeds a null Dimension
    public Dimension getPreferredSize(JComponent c) {
	Dimension	size;
	Insets		border = progressBar.getInsets();
	FontMetrics     fontSizer = progressBar.getFontMetrics(
         	                                  progressBar.getFont());
	
	if (progressBar.getOrientation() == JProgressBar.HORIZONTAL) {
// new Dimension( null ) !!
	    size = new Dimension(getPreferredInnerHorizontal());
...
into the new Dimension(..) which actually fails.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Use some default values, or have any fallback strategy, however no NPE

ERROR MESSAGES/STACK TRACES THAT OCCUR :

java.lang.NullPointerException
	at java.awt.Dimension.<init>(Dimension.java:91)
	at javax.swing.plaf.basic.BasicProgressBarUI.getPreferredSize(BasicProgressBarUI.java:757)
	at javax.swing.JComponent.getPreferredSize(JComponent.java:1582)
	at java.awt.GridBagLayout.GetLayoutInfo(GridBagLayout.java:911)
	at java.awt.GridBagLayout.getLayoutInfo(GridBagLayout.java:816)
	at java.awt.GridBagLayout.ArrangeGrid(GridBagLayout.java:1412)
	at java.awt.GridBagLayout.arrangeGrid(GridBagLayout.java:1372)
	at java.awt.GridBagLayout.layoutContainer(GridBagLayout.java:712)
	at java.awt.Container.layout(Container.java:1401)
	at java.awt.Container.doLayout(Container.java:1390)
	at java.awt.Container.validateTree(Container.java:1473)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validateTree(Container.java:1480)
	at java.awt.Container.validate(Container.java:1448)
	at java.awt.Window.show(Window.java:507)
	at java.awt.Component.show(Component.java:1300)
	at java.awt.Component.setVisible(Component.java:1253)


REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
switch XP Style back to default