There is something wrong with the Telerik radScriptManager. substitute the code below and you'll be fine
<asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="True" AsyncPostBackTimeout="360000">
<Scripts>
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js" />
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQueryInclude.js" />
</Scripts>
</asp:ScriptManager>