Vista + AJAX "web wervice is undefined" javascript error

 I have an Ajax enabled web application I am developing with VS 2005 running on a Vista machine. I have created a simple web service just like Joe Stagner's demo video (http://www.asp.net/learn/ajax-videos/video-79.aspx). I am trying to make a client side call to the web service but I get a 'SimpleService' is undefined error. Everything runs OK on XP and Server 2003 machines. It will be deployed on Server 2003 but I would like to be able to develop and debug on the machine I am sitting in front of. Heres some code:
<script language="javascript" type="text/javascript">

function Button1_onclick() {
ret = SimpleService.SayHello(document.getElementById('Text1').value, OnComplete ...