Any ideas would be great - I hope I provide enough information here.  I'm getting a bit frustrated - I'm a newbie in the .NET programming arena.

Full Error returned from VWD 2005 Express Beta:
Error 1 Could not create type 'VisaValidator.CreditCardValidator'. c:\inetpub\wwwroot\XMLWebServices\Chapter3\VisaValidator\Validation.asmx 1

Environment: Windows XP SP2 with local IIS and other prerequisites.  I confirmed by getting 'Hello World' example to work.

Code (Validation.vb):
Imports System.Web.Services
Imports XMLWebServicesStepByStep.CreditCardValidator
<WebService(Namespace:="http://localhost/", _
Name:="VISAValidator", _
Description:="A service to validate VISA card numbers.")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
Public Class CreditCardValidator
Inherits System.Web.Services.WebService
<WebMethod(Description:="Validate a VISA card number.")> _
Public Function _
ValidateVISACard(ByVal p_card_number As String) _
As Boolean
Try
Return New Validator().ValidateVisa(p_card_number)
Catch x_ex As System.ApplicationException
Return False
End Try
End Function
End Class

Code (Validation.asmx):
<%@ WebService Language="vb" CodeBehind="~/App_Code/Validation.asmx.vb" Class="VisaValidator.CreditCardValidator" %>