Just run SwingSet demo with XAWT and as it comes up, after the splash is gone,
immediately press Shift+F10, and hit escape, keep repeating this until you
get the hang. It happens once in every three tries. It caused a classic circular
deadlock as reported by hotspot below :

Java stack information for the threads listed above:
===================================================
"AWT-EventQueue-0":
        at sun.awt.X11.XBaseWindow.toGlobal(XBaseWindow.java:539)
        - waiting to lock <0x499436a0> (a java.lang.Class)
        at sun.awt.X11.XBaseWindow.toGlobal(XBaseWindow.java:555)
        at sun.awt.X11.XWindow.getLocationOnScreen(XWindow.java:879)
        at java.awt.Component.getLocationOnScreen_NoTreeLock(Component.java:1656
)
        at java.awt.Component.getLocationOnScreen(Component.java:1641)
        - locked <0x45c15f70> (a java.awt.Component$AWTTreeLock)
        at javax.swing.JPopupMenu.show(JPopupMenu.java:973)
        at SwingSet2$ActivatePopupMenuAction.actionPerformed(SwingSet2.java:1185
)
        at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1592)
        at javax.swing.JComponent.processKeyBinding(JComponent.java:2689)
        at javax.swing.KeyboardManager.fireBinding(KeyboardManager.java:255)
        at javax.swing.KeyboardManager.fireKeyboardAction(KeyboardManager.java:2
04)
        at javax.swing.JComponent.processKeyBindingsForAllComponents(JComponent.
java:2766)
        at javax.swing.JComponent.processKeyBindings(JComponent.java:2758)
        at javax.swing.JComponent.processKeyEvent(JComponent.java:2652)
        at java.awt.Component.processEvent(Component.java:5240)
        at java.awt.Container.processEvent(Container.java:1961)
        at java.awt.Component.dispatchEventImpl(Component.java:3931)
        at java.awt.Container.dispatchEventImpl(Container.java:2019)
        at java.awt.Component.dispatchEvent(Component.java:3779)
        at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.ja
va:1804)
        at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboard
FocusManager.java:668)
        at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeybo
ardFocusManager.java:916)
        at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeybo
ardFocusManager.java:794)
        at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFoc
usManager.java:632)
        at java.awt.Component.dispatchEventImpl(Component.java:3817)
        at java.awt.Container.dispatchEventImpl(Container.java:2019)
        at java.awt.Window.dispatchEventImpl(Window.java:1739)
        at java.awt.Component.dispatchEvent(Component.java:3779)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
read.java:231)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:163)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
"AWT-XAWT":
        at sun.awt.X11.XToolkit.getParentFramePeer(XToolkit.java:424)
        - waiting to lock <0x45c15f70> (a java.awt.Component$AWTTreeLock)
        at sun.awt.X11.XWindow.handleKeyPress(XWindow.java:776)
        at sun.awt.X11.XBaseWindow.dispatchEvent(XBaseWindow.java:783)
        at sun.awt.X11.XBaseWindow.dispatchToWindow(XBaseWindow.java:749)
        at sun.awt.X11.XToolkit.dispatchEvent(XToolkit.java:394)
        at sun.awt.X11.XToolkit.run(XToolkit.java:493)
        at sun.awt.X11.XToolkit.run(XToolkit.java:438)
        at java.lang.Thread.run(Thread.java:565)

Found 1 deadlock.


Rest of the Threads :

Full thread dump Java HotSpot(TM) Client VM (1.5.0-beta-b30 mixed mode):

"DestroyJavaVM" prio=1 tid=0x0805a8e0 nid=0x5ad1 waiting on condition [0x0000000
0..0xbfffb170]

"Thread-1" prio=1 tid=0x083bac70 nid=0x5ae3 waiting for monitor entry [0xbdbfe00
0..0xbdbff57c]
        at java.awt.Container.getComponent(Container.java:277)
        - waiting to lock <0x45c15f70> (a java.awt.Component$AWTTreeLock)
        at javax.swing.JViewport.getView(JViewport.java:932)
        at javax.swing.JViewport.scrollRectToVisible(JViewport.java:344)
        at javax.swing.JComponent.scrollRectToVisible(JComponent.java:2903)
        at javax.swing.JList.ensureIndexIsVisible(JList.java:953)
        at javax.swing.plaf.basic.BasicComboPopup.setListSelection(BasicComboPop
up.java:1110)
        at javax.swing.plaf.basic.BasicComboPopup.access$200(BasicComboPopup.jav
a:46)
        at javax.swing.plaf.basic.BasicComboPopup$Handler.itemStateChanged(Basic
ComboPopup.java:947)
        at javax.swing.JComboBox.fireItemStateChanged(JComboBox.java:1162)
        at javax.swing.JComboBox.selectedItemChanged(JComboBox.java:1219)
        at javax.swing.JComboBox.contentsChanged(JComboBox.java:1266)
        at javax.swing.AbstractListModel.fireContentsChanged(AbstractListModel.j
ava:100)
        at javax.swing.DefaultComboBoxModel.setSelectedItem(DefaultComboBoxModel
.java:88)
        at javax.swing.JComboBox.setSelectedItem(JComboBox.java:551)
        at ComboBoxDemo.actionPerformed(ComboBoxDemo.java:358)
        at javax.swing.JComboBox.fireActionEvent(JComboBox.java:1197)
        at javax.swing.JComboBox.setSelectedItem(JComboBox.java:561)
        at javax.swing.JComboBox.setSelectedIndex(JComboBox.java:597)
        at ComboBoxDemo.createComboBoxDemo(ComboBoxDemo.java:202)
        at ComboBoxDemo.<init>(ComboBoxDemo.java:92)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstruct
orAccessorImpl.java:39)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingC
onstructorAccessorImpl.java:27)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:414)
        at SwingSet2.loadDemo(SwingSet2.java:790)
        at SwingSet2.loadDemos(SwingSet2.java:93)
        at SwingSet2$DemoLoadThread.run(SwingSet2.java:1344)

"Image Fetcher 1" daemon prio=1 tid=0x08360b28 nid=0x5ae2 in Object.wait() [0xbd
dff000..0xbddff4fc]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45c455c8> (a java.util.Vector)
        at sun.awt.image.ImageFetcher.nextImage(ImageFetcher.java:114)
        - locked <0x45c455c8> (a java.util.Vector)
        at sun.awt.image.ImageFetcher.fetchloop(ImageFetcher.java:167)
        at sun.awt.image.ImageFetcher.run(ImageFetcher.java:136)

"Image Fetcher 0" daemon prio=1 tid=0x08407a00 nid=0x5ae1 in Object.wait() [0xbd
fff000..0xbdfff67c]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45c455c8> (a java.util.Vector)
        at sun.awt.image.ImageFetcher.nextImage(ImageFetcher.java:114)
        - locked <0x45c455c8> (a java.util.Vector)
        at sun.awt.image.ImageFetcher.fetchloop(ImageFetcher.java:167)
        at sun.awt.image.ImageFetcher.run(ImageFetcher.java:136)

"TimerQueue" daemon prio=1 tid=0x080def90 nid=0x5ae0 in Object.wait() [0xbe5ff00
0..0xbe5ff5fc]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45dc99e0> (a javax.swing.TimerQueue)
        at javax.swing.TimerQueue.run(TimerQueue.java:233)
        - locked <0x45dc99e0> (a javax.swing.TimerQueue)
        at java.lang.Thread.run(Thread.java:565)

"AWT-EventQueue-0" prio=1 tid=0x083df3a8 nid=0x5ade waiting for monitor entry [0
xbe1fe000..0xbe1ff77c]
        at sun.awt.X11.XBaseWindow.toGlobal(XBaseWindow.java:539)
        - waiting to lock <0x499436a0> (a java.lang.Class)
        at sun.awt.X11.XBaseWindow.toGlobal(XBaseWindow.java:555)
        at sun.awt.X11.XWindow.getLocationOnScreen(XWindow.java:879)
        at java.awt.Component.getLocationOnScreen_NoTreeLock(Component.java:1656
)
        at java.awt.Component.getLocationOnScreen(Component.java:1641)
        - locked <0x45c15f70> (a java.awt.Component$AWTTreeLock)
        at javax.swing.JPopupMenu.show(JPopupMenu.java:973)
        at SwingSet2$ActivatePopupMenuAction.actionPerformed(SwingSet2.java:1185
)
        at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1592)
        at javax.swing.JComponent.processKeyBinding(JComponent.java:2689)
        at javax.swing.KeyboardManager.fireBinding(KeyboardManager.java:255)
        at javax.swing.KeyboardManager.fireKeyboardAction(KeyboardManager.java:2
04)
        at javax.swing.JComponent.processKeyBindingsForAllComponents(JComponent.
java:2766)
        at javax.swing.JComponent.processKeyBindings(JComponent.java:2758)
        at javax.swing.JComponent.processKeyEvent(JComponent.java:2652)
        at java.awt.Component.processEvent(Component.java:5240)
        at java.awt.Container.processEvent(Container.java:1961)
        at java.awt.Component.dispatchEventImpl(Component.java:3931)
        at java.awt.Container.dispatchEventImpl(Container.java:2019)
        at java.awt.Component.dispatchEvent(Component.java:3779)
        at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.ja
va:1804)
        at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboard
FocusManager.java:668)
        at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeybo
ardFocusManager.java:916)
        at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeybo
ardFocusManager.java:794)
        at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFoc
usManager.java:632)
        at java.awt.Component.dispatchEventImpl(Component.java:3817)
        at java.awt.Container.dispatchEventImpl(Container.java:2019)
        at java.awt.Window.dispatchEventImpl(Window.java:1739)
        at java.awt.Component.dispatchEvent(Component.java:3779)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchTh
        read.java:231)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThre
ad.java:163)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)

"AWT-Shutdown" prio=1 tid=0x083de0e0 nid=0x5add in Object.wait() [0xbe3ff000..0x
be3ff6fc]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45c3ae28> (a java.lang.Object)
        at java.lang.Object.wait(Object.java:468)
        at sun.awt.AWTAutoShutdown.run(AWTAutoShutdown.java:259)
        - locked <0x45c3ae28> (a java.lang.Object)
        at java.lang.Thread.run(Thread.java:565)

"AWT-XAWT" daemon prio=1 tid=0x083a94f8 nid=0x5adb waiting for monitor entry [0x
be7ff000..0xbe7ff7fc]
        at sun.awt.X11.XToolkit.getParentFramePeer(XToolkit.java:424)
        - waiting to lock <0x45c15f70> (a java.awt.Component$AWTTreeLock)
        at sun.awt.X11.XWindow.handleKeyPress(XWindow.java:776)
        at sun.awt.X11.XBaseWindow.dispatchEvent(XBaseWindow.java:783)
        at sun.awt.X11.XBaseWindow.dispatchToWindow(XBaseWindow.java:749)
        at sun.awt.X11.XToolkit.dispatchEvent(XToolkit.java:394)
        at sun.awt.X11.XToolkit.run(XToolkit.java:493)
        at sun.awt.X11.XToolkit.run(XToolkit.java:438)
        at java.lang.Thread.run(Thread.java:565)

"Java2D Disposer" daemon prio=1 tid=0x081ba408 nid=0x5ada in Object.wait() [0xbe
9ff000..0xbe9ff57c]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45c36590> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:116)
        - locked <0x45c36590> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:132)
        at sun.java2d.Disposer.run(Disposer.java:107)
        at java.lang.Thread.run(Thread.java:565)

"Low Memory Detector" daemon prio=1 tid=0x080c9138 nid=0x5ad8 runnable [0x000000
00..0x00000000]

"CompilerThread0" daemon prio=1 tid=0x080c7de8 nid=0x5ad7 waiting on condition [
0x00000000..0xbeffeff4]

"Signal Dispatcher" daemon prio=1 tid=0x080c3f50 nid=0x5ad6 waiting on condition
 [0x00000000..0x00000000]

"Finalizer" daemon prio=1 tid=0x080bbb98 nid=0x5ad5 in Object.wait() [0xbf3ff000
..0xbf3ff6fc]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45c15478> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:116)
        - locked <0x45c15478> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:132)
        at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:159)

"Reference Handler" daemon prio=1 tid=0x080bae58 nid=0x5ad4 in Object.wait() [0x
bf5ff000..0xbf5ff87c]
        at java.lang.Object.wait(Native Method)
        - waiting on <0x45c152f0> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:468)
        at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:118)
        - locked <0x45c152f0> (a java.lang.ref.Reference$Lock)

"VM Thread" prio=1 tid=0x080b6450 nid=0x5ad3 runnable

"VM Periodic Task Thread" prio=1 tid=0x080ca428 nid=0x5ad9 waiting on condition