Actually, while I typed up this question I let it sit frozen for a while and it unfroze. In the Command Window I found the following exception text:
Exception in thread "AWT-EventQueue-0" com.teamdev.jxbrowser.chromium.internal.ipc.IPCException: Failed to execute shutdown post message.
at com.teamdev.jxbrowser.chromium.internal.ipc.IPC.c(Unknown Source)
at com.teamdev.jxbrowser.chromium.internal.ipc.IPC.stop(Unknown Source)
at com.teamdev.jxbrowser.chromium.Browser.a(Unknown Source)
at com.teamdev.jxbrowser.chromium.Browser.dispose(Unknown Source)
at com.mathworks.html.jxbrowser.chromium.JxBrowserChromiumComponent.doBrowserDisposal(JxBrowserChromiumComponent.java:96)
at com.mathworks.html.jxbrowser.chromium.JxBrowserChromiumComponent.access$400(JxBrowserChromiumComponent.java:20)
at com.mathworks.html.jxbrowser.chromium.JxBrowserChromiumComponent$RemoveRunnable.run(JxBrowserChromiumComponent.java:82)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)