java.util.ConcurrentModificationException
        at java.util.Hashtable$Enumerator.next(Hashtable.java:1031)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.compileDefaults(NimbusStyle.java:378)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.validate(NimbusStyle.java:297)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.getValues(NimbusStyle.java:927)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.getInsets(NimbusStyle.java:605)
        at javax.swing.plaf.synth.SynthStyle.installDefaults(SynthStyle.java:896)
        at javax.swing.plaf.synth.SynthLookAndFeel.updateStyle(SynthLookAndFeel.java:276)
        at javax.swing.plaf.synth.SynthMenuBarUI.updateStyle(SynthMenuBarUI.java:58)
        at javax.swing.plaf.synth.SynthMenuBarUI.installDefaults(SynthMenuBarUI.java:47)
        at javax.swing.plaf.basic.BasicMenuBarUI.installUI(BasicMenuBarUI.java:56)
        at javax.swing.JComponent.setUI(JComponent.java:673)
        at javax.swing.JMenuBar.setUI(JMenuBar.java:118)
        at javax.swing.JMenuBar.updateUI(JMenuBar.java:127)
        at org.openide.awt.MenuBar.updateUI(MenuBar.java:168)
        at org.openide.awt.MenuBar$1.run(MenuBar.java:155)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:125)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)