Opening a window with an external page via JavaScript shows a blank page, raw HTML work though

[paul-2011]

Hi, I'm able to load external pages inside a window when I use html components but when using Ext.Net components the window displays blank, could you please take a quick look at the code snippet bellow?
I can load just the external page on the browser and it displays my Ext.Net components without a problem.
I'm using Ext.Net 2.3.
Thanks

new Ext.Window({
                id: "wndExternal",
                title: "External",
                width: 640,
                height: 480,
                maximizable: false,
                minimizable: false,
                resizable: false,
                modal: true,
                closeAction: 'close',
                autoLoad: {
                    url: "externalwindow.aspx", mode: "iframe", showMask: true
                }
            });