On the report form, add a script manager from the toolbox before the report control: open the toolbox and select Ajax Extensions - Script Manager, then drag it onto the form. Using Visual Studio 2012, what I ended up with was the following new control on the form:

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>

Full details for Visual Studio 2012 at http://msdn.microsoft.com/en-us/library/ms252104.aspx