Google maps, where is my code faulty?

Question

I don't understand what is wrong? is it my Xelement call or is my flex file incorrect?

private void button2_Click(object sender, RoutedEventArgs e) {

        XElement call = new XElement("invoke",
                new XAttribute("name", "clearMarkers"),
                new XAttribute("returntype", "xml"));

        try 
        {
            axFlash.CallFunction(call.ToString(SaveOptions.DisableFormatting));
        }
        catch (Exception error)
        {
            MessageBox.Show(e.ToString());
        }

    }

mxml file:

private function clearMarkers():void
            {
                clearOverlays();
            }

Exception:

A first chance exception of type 'System.Runtime.InteropServices.COMException' occurred in AxInterop.ShockwaveFlashObjects.dll System.Runtime.InteropServices.COMException (0x80004005): Error HRESULT E_FAIL has been returned from a call to a COM component. at ShockwaveFlashObjects.IShockwaveFlash.CallFunction(String request) at AxShockwaveFlashObjects.AxShockwaveFlash.CallFunction(String request) at GoogleMapsFlashInWpf.Window1.button2_Click(Object sender, RoutedEventArgs e) in C:\Users\Paul\Documents\Visual Studio 2010\Projects\GoogleMapsFlashInWpf\GoogleMapsFlashInWpf\MainWindow.xaml.cs:line 287