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Which version of ASP.NET AJAX are you using? Beta 2?

FYI, in Beta 2, in order for your web service to be callable from the client, you need to add the ScriptService() attribute class to the WebService class to indicate that the Web service can be invoked from script:

<WebService(Namespace:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
<Microsoft.Web.Script.Services.ScriptService()> _
Public Class WebService
Inherits System.Web.Services.WebService

regards,
Wei-Meng Lee