Reproduction:

- Extract the attached test case.
- Execute the swing test case.
  % cd swingtest/classes
  % java SwingTest -command abc
- Hold between 2 rows on swing.JTable test component and
  drag horizontally to change the row width.

The following exception was thrown.

java.lang.ClassCastException: javax.swing.JPanel
        at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseDragged(BasicTableHeaderUI.java:146)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:260)
        at java.awt.Component.processMouseMotionEvent(Component.java:5068)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:2790)
        at java.awt.Component.processEvent(Component.java:4823)
        at java.awt.Container.processEvent(Container.java:1383)
        at java.awt.Component.dispatchEventImpl(Component.java:3527)
        at java.awt.Container.dispatchEventImpl(Container.java:1440)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3219)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2951)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2866)
        at java.awt.Container.dispatchEventImpl(Container.java:1426)
        at java.awt.Window.dispatchEventImpl(Window.java:1568)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:193)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:147)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:141)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:133)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:101)
java.lang.ClassCastException: javax.swing.JPanel
        at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseDragged(BasicTableHeaderUI.java:146)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:260)
        at java.awt.Component.processMouseMotionEvent(Component.java:5068)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:2790)
        at java.awt.Component.processEvent(Component.java:4823)
        at java.awt.Container.processEvent(Container.java:1383)
        at java.awt.Component.dispatchEventImpl(Component.java:3527)
        at java.awt.Container.dispatchEventImpl(Container.java:1440)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3219)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2951)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2866)
        at java.awt.Container.dispatchEventImpl(Container.java:1426)
        at java.awt.Window.dispatchEventImpl(Window.java:1568)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:193)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:147)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:141)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:133)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:101)
java.lang.ClassCastException: javax.swing.JPanel
        at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseDragged(BasicTableHeaderUI.java:146)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:260)
        at java.awt.Component.processMouseMotionEvent(Component.java:5068)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:2790)
        at java.awt.Component.processEvent(Component.java:4823)
        at java.awt.Container.processEvent(Container.java:1383)
        at java.awt.Component.dispatchEventImpl(Component.java:3527)
        at java.awt.Container.dispatchEventImpl(Container.java:1440)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3219)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2951)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2866)
        at java.awt.Container.dispatchEventImpl(Container.java:1426)
        at java.awt.Window.dispatchEventImpl(Window.java:1568)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:193)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:147)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:141)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:133)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:101)
java.lang.ClassCastException: javax.swing.JPanel
        at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseDragged(BasicTableHeaderUI.java:146)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:260)
        at java.awt.Component.processMouseMotionEvent(Component.java:5068)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:2790)
        at java.awt.Component.processEvent(Component.java:4823)
        at java.awt.Container.processEvent(Container.java:1383)
        at java.awt.Component.dispatchEventImpl(Component.java:3527)
        at java.awt.Container.dispatchEventImpl(Container.java:1440)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3219)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2951)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2866)
        at java.awt.Container.dispatchEventImpl(Container.java:1426)
        at java.awt.Window.dispatchEventImpl(Window.java:1568)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:193)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:147)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:141)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:133)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:101)
java.lang.ClassCastException: javax.swing.JPanel
        at javax.swing.plaf.basic.BasicTableHeaderUI$MouseInputHandler.mouseDragged(BasicTableHeaderUI.java:146)
        at java.awt.AWTEventMulticaster.mouseDragged(AWTEventMulticaster.java:260)
        at java.awt.Component.processMouseMotionEvent(Component.java:5068)
        at javax.swing.JComponent.processMouseMotionEvent(JComponent.java:2790)
        at java.awt.Component.processEvent(Component.java:4823)
        at java.awt.Container.processEvent(Container.java:1383)
        at java.awt.Component.dispatchEventImpl(Component.java:3527)
        at java.awt.Container.dispatchEventImpl(Container.java:1440)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:3219)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:2951)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:2866)
        at java.awt.Container.dispatchEventImpl(Container.java:1426)
        at java.awt.Window.dispatchEventImpl(Window.java:1568)
        at java.awt.Component.dispatchEvent(Component.java:3368)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:193)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:147)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:141)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:133)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:101)

This problem is not reproducible on merlin beta2 (b77).

###@###.### 2001-10-02