First of first check your Telerik version, it should be equal or greater (2010.1.309.35)
If your version is less then update your telerik and install your system. then open your visual studio project , when you open then telerik automatically ask to you for update your vesrion in your existing Project.
then remove radscriptmanager from Master pages. and only add
asp:ToolkitScriptManager ID="ToolkitScriptManagerMaster" runat="server">
its working very smoothly.