FULL PRODUCT VERSION :
java version "1.6.0-ea"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-ea-b53)
Java HotSpot(TM) Client VM (build 1.6.0-ea-b53, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

EXTRA RELEVANT SYSTEM CONFIGURATION :
nVidia graphic card

A DESCRIPTION OF THE PROBLEM :
Attempting to open a Swing Menu causes a fatal error and the JVM exits when -Xcheck:jni is specified.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run a swing app e.g. SwingSet2.jar with the -Xcheck:jni option.
Attempt to activate a pull down menu.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
no fatal error
ACTUAL -
FATAL ERROR in native method: Field type (instance) mismatch in JNI get/set field operations

application exits.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
FATAL ERROR in native method: Field type (instance) mismatch in JNI get/set field operations
        at sun.awt.windows.WWindowPeer.nativeGrab(Native Method)
        at sun.awt.windows.WWindowPeer.grab(Unknown Source)
        at sun.awt.windows.WToolkit.grab(Unknown Source)
        at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabber.grabWindow(Unknown Source)
        at javax.swing.plaf.basic.BasicPopupMenuUI$MouseGrabber.stateChanged(Unknown Source)
        at javax.swing.MenuSelectionManager.fireStateChanged(Unknown Source)
        at javax.swing.MenuSelectionManager.setSelectedPath(Unknown Source)
        at javax.swing.plaf.basic.BasicMenuUI$Handler.mousePressed(Unknown Source)
        at java.awt.Component.processMouseEvent(Unknown Source)
        at javax.swing.JComponent.processMouseEvent(Unknown Source)
        at java.awt.Component.processEvent(Unknown Source)
        at java.awt.Container.processEvent(Unknown Source)
        at java.awt.Component.dispatchEventImpl(Unknown Source)
        at java.awt.Container.dispatchEventImpl(Unknown Source)
        at java.awt.Component.dispatchEvent(Unknown Source)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
        at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
        at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
        at java.awt.Container.dispatchEventImpl(Unknown Source)
        at java.awt.Window.dispatchEventImpl(Unknown Source)
        at java.awt.Component.dispatchEvent(Unknown Source)
        at java.awt.EventQueue.dispatchEvent(Unknown Source)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
        at java.awt.EventDispatchThread.run(Unknown Source)

REPRODUCIBILITY :
This bug can be reproduced always.

Release Regression From : 5.0u5
The above release value was the last known release where this
bug was known to work. Since then there has been a regression.