This is actually from bug 4455101, submitter was reporting a different problem, which is why I'm filing this as a separate bug. I've attched the test case from that bug. To reproduce it, do the following:
If you do the following:
  click on the first Menu
  click on the sub menu 'Menu'
  click on its sub menu 'Menu'
then the CPU becomes pegged and the app is unable to do anything. Here is the state of the threads at this
point:

Full thread dump:

"TimerQueue" daemon prio=5 tid=0x158da8 nid=0x11 waiting on monitor [70381000..70381a28]
at java.lang.Object.wait(Native Method)
- waiting on <74d63d88> (a javax.swing.TimerQueue)
at javax.swing.TimerQueue.run(TimerQueue.java:234)
- locked <74d63d88> (a javax.swing.TimerQueue)
at java.lang.Thread.run(Thread.java:579)

"Thread-3" prio=5 tid=0x28ae0 nid=0x1 waiting on monitor [0..ffbee3d0]

"AWT-EventQueue-0" prio=6 tid=0x1e6868 nid=0x10 waiting for monitor entry [74501000..74501a28]
at java.awt.AWTEvent.nativeSetSource(Native Method)
at java.awt.AWTEvent.setSource(AWTEvent.java:271)
- locked <74d8cb10> (a java.awt.event.FocusEvent)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:443)
at java.awt.Component.dispatchEventImpl(Component.java:3367)
at java.awt.Container.dispatchEventImpl(Container.java:1399)
at java.awt.Window.dispatchEventImpl(Window.java:1459)
at java.awt.Component.dispatchEvent(Component.java:3343)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:439)
at java.awt.SequencedEvent.dispatch(SequencedEvent.java:96)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:437)
at java.awt.EventDispatchThread.pumpOneEvent(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:131)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

"Thread-1" daemon prio=5 tid=0xdca98 nid=0xf waiting on monitor [74601000..74601a28]
at java.lang.Object.wait(Native Method)
- waiting on <74d39b90> (a java.util.TaskQueue)
at java.util.TimerThread.mainLoop(Timer.java:432)
- locked <74d39b90> (a java.util.TaskQueue)
at java.util.TimerThread.run(Timer.java:385)

"AWT-Shutdown" prio=6 tid=0xd78c8 nid=0xe waiting on monitor [74801000..74801a28]
at java.lang.Object.wait(Native Method)
- waiting on <74e10118> (a java.lang.Object)
at java.lang.Object.wait(Object.java:425)
at sun.awt.AWTAutoShutdown.run(AWTAutoShutdown.java:262)
- locked <74e10118> (a java.lang.Object)
at java.lang.Thread.run(Thread.java:579)

"AWT-Motif" daemon prio=6 tid=0x111b60 nid=0xd runnable [74701000..74701a28]
at sun.awt.motif.MToolkit.run(Native Method)
at java.lang.Thread.run(Thread.java:579)

"Signal Dispatcher" daemon prio=10 tid=0x98c68 nid=0xa waiting on monitor [0..0]

"Finalizer" daemon prio=8 tid=0x94f18 nid=0x7 waiting on monitor [7d381000..7d381a28]
at java.lang.Object.wait(Native Method)
- waiting on <74e10218> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:111)
- locked <74e10218> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:126)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:162)

"Reference Handler" daemon prio=10 tid=0x93690 nid=0x6 waiting on monitor [7e981000..7e981a28]
at java.lang.Object.wait(Native Method)
- waiting on <74e10278> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:425)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:110)
- locked <74e10278> (a java.lang.ref.Reference$Lock)

"VM Thread" prio=5 tid=0x92358 nid=0x4 runnable

"VM Periodic Task Thread" prio=10 tid=0x97490 nid=0x8 waiting on monitor
"Suspend Checker Thread" prio=10 tid=0x98380 nid=0x9 runnable