java.lang.ClassNotFoundException: From file: MultiFileObject@13fc5f6[Menu/Edit/Separator1.instance] due to: java.util.ConcurrentModificationException
        at org.openide.loaders.InstanceSupport.instanceClass(InstanceSupport.java:159)
        at org.openide.loaders.InstanceDataObject$Ser.instanceClass(InstanceDataObject.java:1204)
        at org.openide.loaders.InstanceDataObject.instanceClass(InstanceDataObject.java:727)
        at org.openide.awt.MenuBar$LazyMenu$MenuFolder.acceptCookie(MenuBar.java:637)
        at org.openide.loaders.FolderInstance.acceptDataObject(FolderInstance.java:420)
        at org.openide.loaders.FolderInstance.defaultProcessObjects(FolderInstance.java:767)
        at org.openide.loaders.FolderInstance.access$000(FolderInstance.java:101)
        at org.openide.loaders.FolderInstance$1R.init(FolderInstance.java:685)
        at org.openide.loaders.FolderInstance$1R.run(FolderInstance.java:712)
        at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:573)
        at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:1005)