Type and Sys not defined JavaScript error

I'm trying to follow a simple example of AJAX-enabled WCF Service like: http://www.pluralsight.com/community/blogs/fritz/archive/2008/01/31/50121.aspx

I'm getting the JavaScript errors Type not defined and Sys not defined. Does this mean there is an issue with one of these .axd things? or something else? How do I troubleshoot what is wrong with the Ajax scripts?

From stackoverflow

• Ok. I think I got this one.

  Added this to my web.config

  <httpHandlers>
  <add verb="GET,HEAD" path="ScriptResource.axd"           
       type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" validate="false"/>    
  </httpHandlers>