Only Web services with a [ScriptService] attribute on the class definition can be called from script.

I am trying to use the Slide Show Extender to show some photos and I followed step by step the online video tutorial on this site and I can't get it to work. I know that you have to un-comment the line that says <System.Web.Script.ScriptService()>_ but it still won't work. I have looked up this error all over the internet and cannot find the solution to what is hapening to my page. Ok...
 I have a Web Service in SlideShowService.asmx with a method called GetSlides().  The page does display and the play button on the form does change from "Play" to "Pause" but it only shows the picture that is set in the <asp:image> tag. Below is the code....What is missing??  TilePhotos.aspx<%@ Page Language="VB" MasterPageFile="~/MasterPage.master" Title="Untitled Page" %> <%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxCon ...