doOverlapped with gmaps doesn't work in firefox - do i something wrong or is it a bug?

test.zul

<zk xmlns="http://www.zkoss.org/2005/zul"
	xmlns:h="http://www.w3.org/1999/xhtml" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://www.zkoss.org/2005/zul http://www.zkoss.org/2005/zul/zul.xsd">
	<window  
	    id = "test"
		border="normal" 
		sizable="true"
		maximizable="true"
		use="ui.TestWindow"
	>
	<script src="http://maps.google.com/maps?file=api&v=2&key=<<MY_KEY>>" type="text/javascript"></script>
	<button id="btnDoOverlapped" label="doOverlapped" />
	<button id="btnSendRedirect" label="sendRedirect" />
	</window>
</zk>

ui.TestWindow.java

package ui;

import org.zkoss.zk.ui.Component;
import org.zkoss.zk.ui.Executions;
import org.zkoss.zk.ui.event.Event;
import org.zkoss.zk.ui.event.EventListener;
import org.zkoss.zk.ui.event.Events;
import org.zkoss.zul.Button;
import org.zkoss.zul.Window;

@SuppressWarnings("serial")
public class TestWindow extends Window {
		public void onCreate() {
			//
			Button b = (Button) getFellow("btnDoOverlapped");
			EventListener myListener = new DoOverlappedEventListener();
			b.addEventListener(Events.ON_CLICK, myListener);
			//
			b = (Button) getFellow("btnSendRedirect");
			myListener = new sendRedirectEventListener();
			b.addEventListener(Events.ON_CLICK, myListener);
		}

		public class DoOverlappedEventListener implements EventListener {
		    public boolean isAsap() {
	      		return true;
	      	}
	      	public void onEvent(Event event) {
				Component comp = (Component) Executions.createComponents("test2.zul", null, null);
				Window window = (Window)comp.getFellow("test2");
				window.doOverlapped();
	      	}
		}

		public class sendRedirectEventListener implements EventListener {
		    public boolean isAsap() {
	      		return true;
	      	}
	      	public void onEvent(Event event) {
				Executions.sendRedirect("test2.zul");
	      	}
		}
}

test2.zul

<zk xmlns="http://www.zkoss.org/2005/zul"
	xmlns:h="http://www.w3.org/1999/xhtml" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://www.zkoss.org/2005/zul http://www.zkoss.org/2005/zul/zul.xsd">
	<window  
	    id="test2"
		border="normal" 
		width="100%"
		height="100%"
		sizable="true"
		maximizable="true"
	>
	<script src="http://maps.google.com/maps?file=api&v=2&key=<<MY_KEY>>" type="text/javascript"></script>
	<gmaps id="gmapDetail" width="500px" height="400px" showSmallCtrl="true" showTypeCtrl="true" lat="48" lng="11" zoom="17"/>
	<button id="btn" label="open" />
	</window>
</zk>