Its very easy to generate this NullPointerException.

steps to regenerate this NPE:
1) start a jconsole on solaris-sparc machine.
2) start a go to Mbeans Tab,
3) Open Threading Mbean (Tree->java.lang->Threading)
4) Default opens with Attributes Tab.
5) click on value of "AllLockedMonitors" or
   "AllLockedSynchronizers's" vlaue you will get this NPE on the console.

The same was not happening in my windows-2000 machine,
It displays a navigation menu properly.

An png file of this was attached with this bug (solaris-sparc-only-mbean.png).

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XArrayOpenType.getName(XOpenTypeViewer.java:490)
        at com.sun.java.swing.plaf.gtk.GTKPainter.getInsets(GTKPainter.java:52)
        at com.sun.java.swing.plaf.gtk.GTKStyle.getInsets(GTKStyle.java:261)
        at javax.swing.plaf.synth.SynthStyle.installDefaults(SynthStyle.java:848)
        at javax.swing.plaf.synth.SynthLookAndFeel.updateStyle(SynthLookAndFeel.java:244)
        at javax.swing.plaf.synth.SynthTableUI.updateStyle(SynthTableUI.java:104)
        at javax.swing.plaf.synth.SynthTableUI.installDefaults(SynthTableUI.java:88)
        at javax.swing.plaf.basic.BasicTableUI.installUI(BasicTableUI.java:1331)
        at javax.swing.JComponent.setUI(JComponent.java:620)
        at javax.swing.JTable.setUI(JTable.java:3525)
        at javax.swing.JTable.updateUI(JTable.java:3581)
        at javax.swing.JTable.<init>(JTable.java:570)
        at javax.swing.JTable.<init>(JTable.java:495)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XOpenTypeData.<init>(XOpenTypeViewer.java:102)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.<init>(XOpenTypeViewer.java:319)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XArrayOpenType.<init>(XOpenTypeViewer.java:423)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.load(XOpenTypeViewer.java:371)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.loadCompositeData(XOpenTypeViewer.java:402)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.<init>(XOpenTypeViewer.java:328)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.load(XOpenTypeViewer.java:364)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.loadCompositeData(XOpenTypeViewer.java:402)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XCompositeData.<init>(XOpenTypeViewer.java:328)
        at sun.tools.jconsole.inspector.XOpenTypeViewer$XTabularData.<init>(XOpenTypeViewer.java:252)
        at sun.tools.jconsole.inspector.XOpenTypeViewer.<init>(XOpenTypeViewer.java:544)
        at sun.tools.jconsole.inspector.XOpenTypeViewer.loadOpenType(XOpenTypeViewer.java:529)
        at sun.tools.jconsole.inspector.XDataViewer.createAttributeViewer(XDataViewer.java:117)
        at sun.tools.jconsole.inspector.XMBeanAttributes.updateZoomedCell(XMBeanAttributes.java:489)
        at sun.tools.jconsole.inspector.XMBeanAttributes$AttributesMouseListener.mousePressed(XMBeanAttributes.java:616)
        at java.awt.AWTEventMulticaster.mousePressed(AWTEventMulticaster.java:222)
        at java.awt.Component.processMouseEvent(Component.java:5952)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3285)
        at java.awt.Component.processEvent(Component.java:5720)
        at java.awt.Container.processEvent(Container.java:1960)
        at java.awt.Component.dispatchEventImpl(Component.java:4365)
        at java.awt.Container.dispatchEventImpl(Container.java:2018)
        at java.awt.Component.dispatchEvent(Component.java:4195)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4222)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3883)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3816)
        at java.awt.Container.dispatchEventImpl(Container.java:2004)
        at java.awt.Window.dispatchEventImpl(Window.java:2210)
        at java.awt.Component.dispatchEvent(Component.java:4195)
        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)