GWT-Ext Panel / Window remove causes javascript error IE 7.0

[GoogleCodeExporter]

Code Tested:
public void onModuleLoad() {
    Panel panel = new Panel();
    Button button = new Button("Click");
    panel.add(button);
    panel.setSize(300, 300);
    button.addListener(new ButtonListenerAdapter() {
        @Override
    public void onClick(Button button, EventObject e) {
        Window window = new Window("Popup Chart");
        window.setSize(500, 500);
        ChartWidget chart = new ChartWidget();
        ChartData cd = new ChartData("Sample Data", "font-size: 11px;
font-family: Verdana; text-align: center;");
        cd.setBackgroundColour("#ffffff");
        Legend legend = new Legend(Position.TOP, true);
        cd.setLegend(legend);
        PieChart pie = new PieChart();
        pie.setAlpha(0.5f);
        pie.setNoLabels(true);
        pie.setTooltip("#label# #val#<br>#percent#");
        pie.setAnimateOnShow(true);
        pie.setGradientFill(true);
        pie.setColours("#ff0000", "#00aa00", "#0000ff", "#ff9900", "#ff00ff");
        pie.addSlices(new PieChart.Slice(50,"Data 1"));
        pie.addSlices(new PieChart.Slice(20, "Data 2"));
        pie.addSlices(new PieChart.Slice(25, "Data 3"));
        pie.addSlices(new PieChart.Slice(10, "Data 4"));
        pie.addSlices(new PieChart.Slice(10, "Data 5"));
        cd.addElements(pie);
        chart.setHeight("98%");
        chart.setChartData(cd);
        window.add(chart);
        window.show();
    }
});             
    new Viewport(panel);
}

What steps will reproduce the problem?
1. Add OFCGWT Chart to Popup window / Panel(GWT-Ext)
2. When Panel / Window is getting removed it throws "Object doesnot support
this property"

What version of the product are you using? On what operating system?
I am using latest version 2.0.1 beta, on windows xp (IE 7.0)

Please provide any additional information below.
In Firefox its working fine.
Haven't tested in other versions of IE/Chrome/Opera.

Original issue reported on code.google.com by karthike...@googlemail.com on 22 Jul 2009 at 10:39