Originally reported on nbusers.  I can reproduce it also:

Hi,

I just installed NB6.0 M10( full version) on Ubuntu 7.04 with Java 6.0 update1 without importing any projects from older
NB installations.

I have created a new VWP project and dragged a gridPanel component on the canvas. By trying to  change the style
property I got the following NullPointerException:

java.lang.NullPointerException
at
org.netbeans.modules.visualweb.propertyeditors.css.StyleBuilderPanel.addPropertyChangeListener(StyleBuilderPanel.java:154)
at javax.swing.plaf.synth.SynthPanelUI.installListeners(SynthPanelUI.java:49)
at javax.swing.plaf.synth.SynthPanelUI.installUI(SynthPanelUI.java:38)
at javax.swing.JComponent.setUI(JComponent.java:668)
at javax.swing.JPanel.setUI(JPanel.java:136)
at javax.swing.JPanel.updateUI(JPanel.java:109)
at javax.swing.JPanel.<init>(JPanel.java:69)
at javax.swing.JPanel.<init>(JPanel.java:92)
at javax.swing.JPanel.<init>(JPanel.java:100)
at org.netbeans.modules.visualweb.propertyeditors.css.StyleBuilderPanel.<init>(StyleBuilderPanel.java:76)
at org.netbeans.modules.visualweb.propertyeditors.css.CssStylePropertyEditor.getCustomEditor(CssStylePropertyEditor.java:41)
at
org.netbeans.modules.visualweb.propertyeditors.binding.ValueBindingPropertyEditor.getCustomEditor(ValueBindingPropertyEditor.java:358)
at org.openide.explorer.propertysheet.PropertyDialogManager.<init>(PropertyDialogManager.java:104)
at org.openide.explorer.propertysheet.CustomEditorAction.actionPerformed(CustomEditorAction.java:195)
at org.openide.explorer.propertysheet.SheetTable.editCellAt(SheetTable.java:963)
at javax.swing.plaf.basic.BasicTableUI$Handler.adjustSelection(BasicTableUI.java:1084)
at javax.swing.plaf.basic.BasicTableUI$Handler.mousePressed(BasicTableUI.java:1014)
at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:263)
at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:262)
at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:262)
at java.awt.Component.processMouseEvent(Component.java:6035)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3260)
at org.openide.explorer.propertysheet.SheetTable.processMouseEvent(SheetTable.java:696)
at java.awt.Component.processEvent(Component.java:5803)
at java.awt.Container.processEvent(Container.java:2058)
at java.awt.Component.dispatchEventImpl(Component.java:4410)
at java.awt.Container.dispatchEventImpl(Container.java:2116)
at java.awt.Component.dispatchEvent(Component.java:4240)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3983)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
at java.awt.Container.dispatchEventImpl(Container.java:2102)
at java.awt.Window.dispatchEventImpl(Window.java:2429)
at java.awt.Component.dispatchEvent(Component.java:4240)
[catch] at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
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)

Looks like a problem with the native L&F support of Java 6.0 update 1 for Linux???

Cheers
Stephan