I just ran jconsole and saw it freeze. CTRL-\ reveals a deadlock:

Found one Java-level deadlock:
=============================
"AWT-EventQueue-0":
  waiting for ownable synchronizer 0xf3aa3648, (a java.util.concurrent.locks.ReentrantLock$NonfairSync),
  which is held by "AWT-XAWT"
"AWT-XAWT":
  waiting to lock monitor 0x082fbd84 (object 0xf3c0dc58, a sun.tools.jconsole.JConsole),
  which is held by "AWT-EventQueue-0"

Java stack information for the threads listed above:
===================================================
"AWT-EventQueue-0":
at sun.misc.Unsafe.park(Native Method)
- parking to wait for <0xf3aa3648> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:769)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:802)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1132)
at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:214)
at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:290)
at sun.awt.SunToolkit.awtLock(SunToolkit.java:269)
at sun.awt.X11.XBaseWindow.updateWMName(XBaseWindow.java:644)
at sun.awt.X11.XDecoratedPeer.updateWMName(XDecoratedPeer.java:192)
at sun.awt.X11.XDecoratedPeer.setTitle(XDecoratedPeer.java:180)
at java.awt.Frame.setTitle(Frame.java:519)
- locked <0xf3c0dc58> (a sun.tools.jconsole.JConsole)
at sun.tools.jconsole.JConsole.createMDI(JConsole.java:187)
at sun.tools.jconsole.JConsole.access$1300(JConsole.java:54)
at sun.tools.jconsole.JConsole$6.run(JConsole.java:807)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:235)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:603)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:286)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:191)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:186)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:178)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:139)
"AWT-XAWT":
at java.awt.Frame.getExtendedState(Frame.java:808)
- waiting to lock <0xf3c0dc58> (a sun.tools.jconsole.JConsole)
at java.awt.Frame.paramString(Frame.java:970)
at javax.swing.JFrame.paramString(JFrame.java:861)
at java.awt.Component.toString(Component.java:7814)
at java.lang.String.valueOf(String.java:2838)
at java.lang.StringBuilder.append(StringBuilder.java:128)
at sun.awt.X11.XDecoratedPeer.requestWindowFocus(XDecoratedPeer.java:1170)
at sun.awt.X11.XDecoratedPeer.handleWmTakeFocus(XDecoratedPeer.java:1041)
at sun.awt.X11.XDecoratedPeer.handleClientMessage(XDecoratedPeer.java:1034)
at sun.awt.X11.XBaseWindow.dispatchEvent(XBaseWindow.java:1074)
at sun.awt.X11.XBaseWindow.dispatchToWindow(XBaseWindow.java:1056)
at sun.awt.X11.XToolkit.dispatchEvent(XToolkit.java:504)
at sun.awt.X11.XToolkit.run(XToolkit.java:599)
at sun.awt.X11.XToolkit.run(XToolkit.java:534)
at java.lang.Thread.run(Thread.java:713)

Found 1 deadlock.

This might be a bug in Swing.