java.util.ConcurrentModificationException
        at java.util.Hashtable$Enumerator.next(Hashtable.java:1031)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.compileDefaults(NimbusStyle.java:378)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.validate(NimbusStyle.java:297)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.getValues(NimbusStyle.java:927)
        at com.sun.java.swing.plaf.nimbus.NimbusStyle.getInsets(NimbusStyle.java:605)
        at javax.swing.plaf.synth.SynthStyle.installDefaults(SynthStyle.java:896)
        at javax.swing.plaf.synth.SynthLookAndFeel.updateStyle(SynthLookAndFeel.java:276)
        at javax.swing.plaf.synth.SynthMenuUI.updateStyle(SynthMenuUI.java:54)
        at javax.swing.plaf.synth.SynthMenuUI.installDefaults(SynthMenuUI.java:42)
        at javax.swing.plaf.basic.BasicMenuItemUI.installUI(BasicMenuItemUI.java:100)
        at javax.swing.JComponent.setUI(JComponent.java:673)
        at javax.swing.AbstractButton.setUI(AbstractButton.java:1782)
        at javax.swing.JMenuItem.setUI(JMenuItem.java:223)
        at javax.swing.JMenu.updateUI(JMenu.java:206)
        at javax.swing.JMenuItem.init(JMenuItem.java:194)
        at javax.swing.JMenuItem.<init>(JMenuItem.java:133)
        at javax.swing.JMenuItem.<init>(JMenuItem.java:110)
        at javax.swing.JMenu.<init>(JMenu.java:158)
        at javax.swing.JMenu.<init>(JMenu.java:148)
        at org.openide.awt.MenuBar$LazyMenu.<init>(MenuBar.java:471)
        at org.openide.awt.MenuBar$MenuBarFolder.acceptFolder(MenuBar.java:382)
        at org.openide.loaders.FolderInstance.acceptDataObject(FolderInstance.java:444)
        at org.openide.loaders.FolderInstance.defaultProcessObjects(FolderInstance.java:780)
        at org.openide.loaders.FolderInstance.access$000(FolderInstance.java:101)
        at org.openide.loaders.FolderInstance$1R.init(FolderInstance.java:698)
        at org.openide.loaders.FolderInstance$1R.run(FolderInstance.java:725)
Caused: org.openide.util.RequestProcessor$SlowItem: task failed due to: java.util.ConcurrentModificationException
        at org.openide.util.RequestProcessor$Task.schedule(RequestProcessor.java:655)
        at org.openide.loaders.FolderInstance.processObjects(FolderInstance.java:753)
        at org.openide.loaders.FolderInstance$Listener.finished(FolderInstance.java:1037)
        at org.openide.loaders.FolderList.createBoth(FolderList.java:901)
        at org.openide.loaders.FolderList.getObjects(FolderList.java:586)
        at org.openide.loaders.FolderList.access$200(FolderList.java:74)
        at org.openide.loaders.FolderList$ListTask.computeResult(FolderList.java:985)
        at org.openide.loaders.FolderList$ListTask.run(FolderList.java:961)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:602)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1084)