Wyjątek ClassCastException

Witam!
Może mi ktoś objaśnić o co chodzi z tym błędem?

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException
        at javax.swing.LayoutComparator.compare(LayoutComparator.java:61)
        at java.util.Arrays.mergeSort(Arrays.java:1270)
        at java.util.Arrays.mergeSort(Arrays.java:1281)
        at java.util.Arrays.mergeSort(Arrays.java:1282)
        at java.util.Arrays.mergeSort(Arrays.java:1282)
        at java.util.Arrays.mergeSort(Arrays.java:1281)
        at java.util.Arrays.sort(Arrays.java:1210)
        at java.util.Collections.sort(Collections.java:159)
        at javax.swing.SortingFocusTraversalPolicy.enumerateAndSortCycle(SortingFocusTraversalPolicy.java:119)
        at javax.swing.SortingFocusTraversalPolicy.getFirstComponent(SortingFocusTraversalPolicy.java:434)
        at javax.swing.LayoutFocusTraversalPolicy.getFirstComponent(LayoutFocusTraversalPolicy.java:148)
        at javax.swing.SortingFocusTraversalPolicy.getDefaultComponent(SortingFocusTraversalPolicy.java:511)
        at java.awt.FocusTraversalPolicy.getInitialComponent(FocusTraversalPolicy.java:152)
        at java.awt.Window.getMostRecentFocusOwner(Window.java:2131)
        at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:629)
        at java.awt.Component.dispatchEventImpl(Component.java:4502)
        at java.awt.Container.dispatchEventImpl(Container.java:2099)
        at java.awt.Window.dispatchEventImpl(Window.java:2478)
        at java.awt.Component.dispatchEvent(Component.java:4460)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.SequencedEvent.dispatch(SequencedEvent.java:101)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
        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)

Pojawia się on podczas wykonywania metody removeAll(), na obiekcie JPanel.

Co najgorsze nie dzieje się to za każdym, tylko w losowych momentach.

Pozdrawiam
Marcin

Przejrzyj źródła klasy LayoutComparator.java.

http://kickjava.com/src/javax/swing/LayoutComparator.java.htm

Wynika, że jakiś tam obiekt nie podpiąłeś do (potomka) Window :)