The Ajax in the sample page is made using:

$find("<%= RadAjaxManager.GetCurrent(Page).ClientID %>").ajaxRequest();

In on the page the AjaxManger updates the panel, in the other the setting is that the proxy should update the panel. This is invalid setting.

<telerik:AjaxSetting AjaxControlID="RadAjaxManagerProxy1" >
    <UpdatedControls>
        <telerik:AjaxUpdatedControl ControlID="rsLeftPanel" LoadingPanelID="ralp1" />
    </UpdatedControls>
</telerik:AjaxSetting>

The correct way of doing this is to use add the settings programatically, or to use the ajaxRequestWithTarget instead of ajaxRequest method
http://docs.telerik.com/devtools/aspnet-ajax/controls/ajax/radajaxmanager/how-to/add-ajaxsettings-programmatically