The problem is reported here: http://forums.java.net/jive/thread.jspa?messageID=322051

The stack trace of the deadlock:

Name: AWT-XAWT
State: BLOCKED on sun.awt.X11.XDialogPeer@25ec1ff7 owned by: AWT-EventQueue-1
Total blocked: 29 Total waited: 1,837

Stack trace:
sun.awt.X11.XWindow.setMouseAbove(XWindow.java:789)
sun.awt.X11.XWindowPeer.setMouseAbove(XWindowPeer.java:1012)
sun.awt.X11.XWindow.leaveNotify(XWindow.java:799)
sun.awt.X11.XWindow.handleXCrossingEvent(XWindow.java:812)
sun.awt.X11.XWindowPeer.handleXCrossingEvent(XWindowPeer.java:1765)
sun.awt.X11.XBaseWindow.dispatchEvent(XBaseWindow.java:1119)
sun.awt.X11.XBaseWindow.dispatchToWindow(XBaseWindow.java:1079)
sun.awt.X11.XToolkit.dispatchEvent(XToolkit.java:475)
sun.awt.X11.XToolkit.run(XToolkit.java:588)
sun.awt.X11.XToolkit.run(XToolkit.java:523)
java.lang.Thread.run(Thread.java:619)

Name: AWT-EventQueue-1
State: WAITING on java.util.concurrent.locks.ReentrantLock$NonfairSync@48f2d715 owned by: AWT-XAWT
Total blocked: 18,133 Total waited: 19,299

Stack trace:
sun.misc.Unsafe.park(Native Method)
java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:747)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:778)
java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1114)
java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
sun.awt.SunToolkit.awtLock(SunToolkit.java:241)
sun.awt.X11.XDropTargetRegistry.unregisterDropSite(XDropTargetRegistry.java:569)
sun.awt.X11.XWindowPeer.removeDropTarget(XWindowPeer.java:1634)
- locked sun.awt.X11.XDialogPeer@25ec1ff7
sun.awt.X11.XComponentPeer.removeDropTarget(XComponentPeer.java:1511)
java.awt.dnd.DropTarget.removeNotify(DropTarget.java:517)
java.awt.Component.removeNotify(Component.java:6721)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
java.awt.Container.removeNotify(Container.java:2611)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
org.openide.explorer.view.ListView$NbList.removeNotify(ListView.java:834)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
org.openide.explorer.view.ListView.removeNotify(ListView.java:607)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
javax.swing.JComponent.removeNotify(JComponent.java:4699)
javax.swing.JRootPane.removeNotify(JRootPane.java:750)
java.awt.Container.removeNotify(Container.java:2604)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
java.awt.Window.removeNotify(Window.java:685)
- locked java.awt.Component$AWTTreeLock@69d8ad6a
org.netbeans.core.windows.services.NbPresenter.removeNotify(NbPresenter.java:349)
java.awt.Window$1DisposeAction.run(Window.java:1013)
java.awt.Window.doDispose(Window.java:1025)
java.awt.Dialog.doDispose(Dialog.java:1248)
java.awt.Window.dispose(Window.java:972)
org.openide.explorer.propertysheet.PropertyDialogManager.actionPerformed(PropertyDialogManager.java:543)
org.netbeans.core.windows.services.NbPresenter$ButtonListener.actionPerformed(NbPresenter.java:1137)
javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
java.awt.Component.processMouseEvent(Component.java:6213)
javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
java.awt.Component.processEvent(Component.java:5978)
java.awt.Container.processEvent(Container.java:2036)
java.awt.Component.dispatchEventImpl(Component.java:4580)
java.awt.Container.dispatchEventImpl(Container.java:2094)
java.awt.Component.dispatchEvent(Component.java:4410)
java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4551)
java.awt.LightweightDispatcher.processMouseEvent(Container.java:4215)
java.awt.LightweightDispatcher.dispatchEvent(Container.java:4145)
java.awt.Container.dispatchEventImpl(Container.java:2080)
java.awt.Window.dispatchEventImpl(Window.java:2475)
java.awt.Component.dispatchEvent(Component.java:4410)
java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:178)
java.awt.Dialog$1.run(Dialog.java:1051)
java.awt.Dialog$3.run(Dialog.java:1103)
java.security.AccessController.doPrivileged(Native Method)
java.awt.Dialog.show(Dialog.java:1101)
org.netbeans.core.windows.services.NbPresenter.superShow(NbPresenter.java:867)
org.netbeans.core.windows.services.NbPresenter.doShow(NbPresenter.java:901)
org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:889)
org.netbeans.core.windows.services.NbPresenter.run(NbPresenter.java:109)
org.openide.util.Mutex.doEventAccess(Mutex.java:1355)
org.openide.util.Mutex.readAccess(Mutex.java:268)
org.netbeans.core.windows.services.NbPresenter.show(NbPresenter.java:874)
java.awt.Component.show(Component.java:1513)
java.awt.Component.setVisible(Component.java:1465)
java.awt.Window.setVisible(Window.java:841)
java.awt.Dialog.setVisible(Dialog.java:991)
org.openide.explorer.propertysheet.CustomEditorAction.actionPerformed(CustomEditorAction.java:318)
org.openide.explorer.propertysheet.SheetTable.processMouseEvent(SheetTable.java:710)
java.awt.Component.processEvent(Component.java:5978)
java.awt.Container.processEvent(Container.java:2036)
java.awt.Component.dispatchEventImpl(Component.java:4580)
java.awt.Container.dispatchEventImpl(Container.java:2094)
java.awt.Component.dispatchEvent(Component.java:4410)
java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4551)
java.awt.LightweightDispatcher.processMouseEvent(Container.java:4212)
java.awt.LightweightDispatcher.dispatchEvent(Container.java:4145)
java.awt.Container.dispatchEventImpl(Container.java:2080)
java.awt.Window.dispatchEventImpl(Window.java:2475)
java.awt.Component.dispatchEvent(Component.java:4410)
java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:104)
java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
java.awt.EventDispatchThread.run(EventDispatchThread.java:122)