NetBeans users are reporting NullPointerException thrown at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth
(XPStyle.java:507) when changing Win OS theme between Win XP style and Win classic style.

Original reports here:
http://www.netbeans.org/issues/show_bug.cgi?id=105790
http://www.netbeans.org/issues/show_bug.cgi?id=121824

Stack trace of an exception:
java.lang.NullPointerException
        at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth(XPStyle.java:507)
        at com.sun.java.swing.plaf.windows.XPStyle$Skin.getWidth(XPStyle.java:511)
        at com.sun.java.swing.plaf.windows.WindowsScrollBarUI.paintThumb(WindowsScrollBarUI.java:175)
        at javax.swing.plaf.basic.BasicScrollBarUI.paint(BasicScrollBarUI.java:366)
        at javax.swing.plaf.ComponentUI.update(ComponentUI.java:143)
        at javax.swing.JComponent.paintComponent(JComponent.java:763)
        at javax.swing.JComponent.paint(JComponent.java:1027)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at org.netbeans.core.windows.view.ui.MultiSplitPane.paint(MultiSplitPane.java:316)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at org.netbeans.core.windows.view.ui.MultiSplitPane.paint(MultiSplitPane.java:316)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at org.netbeans.core.windows.view.ui.MultiSplitPane.paint(MultiSplitPane.java:316)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JLayeredPane.paint(JLayeredPane.java:564)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paint(JComponent.java:1036)
        at javax.swing.JLayeredPane.paint(JLayeredPane.java:564)
        at javax.swing.JComponent.paintChildren(JComponent.java:864)
        at javax.swing.JComponent.paintToOffscreen(JComponent.java:5129)
        at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(RepaintManager.java:1382)
        at javax.swing.RepaintManager$PaintManager.paint(RepaintManager.java:1313)
        at javax.swing.BufferStrategyPaintManager.paint(BufferStrategyPaintManager.java:301)
        at javax.swing.RepaintManager.paint(RepaintManager.java:1128)
        at javax.swing.JComponent.paint(JComponent.java:1013)
        at java.awt.GraphicsCallback$PaintCallback.run(GraphicsCallback.java:21)
        at sun.awt.SunGraphicsCallback.runOneComponent(SunGraphicsCallback.java:60)
        at sun.awt.SunGraphicsCallback.runComponents(SunGraphicsCallback.java:97)
        at java.awt.Container.paint(Container.java:1797)
        at org.netbeans.core.windows.view.ui.MainWindow.paint(MainWindow.java:577)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:734)
        at javax.swing.RepaintManager.paintDirtyRegions(RepaintManager.java:679)
        at javax.swing.RepaintManager.seqPaintDirtyRegions(RepaintManager.java:659)
        at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:128)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)

Unfortunately, error seems to appear randomly, so I don't have any 100% reproducible scenario. Starring at the code, it seems that method getWidth(...) is not prepared to the situation when method getPartSize(...) returns null. So either getPartSize(...) should never return null or getWidth(...) and other methods shoudln't rely on non-null returned value.
Actually I have found a way to reproduce this:
it seems that it is always on switch FROM WindowsXP style.
With NB6 RC1 build, using jdk1.6.0_03

I start with my custom windows theme active. OK.

1. created a NB ee5 web project
2. set Windows Display -> XP style . OK. no exceptions
3. create another NB web project
4. switch Windows display from XP -> Classic
>get the exception

If I switch from XP -> Custom Theme I also get the exception.