Accessing a secure web service

See more:

MS-Access

service

web

I'm new in consuming web services and i have to access a state-run web service.
I was given an app.config file, a certificate file (.cer) and some general instructions.

Haven'n used Visual Studio 2008 Express before but i have 15 years experience in writing vb5/6 code.

Anyway, I installed the .cer file using mmc and then opened a new project and
I added the System.Runtime.Serialization and System.ServiceModel
I addedd a service reference to the WSDL link
I included app.config file in my project
and wrote the follwing code.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace EchoSvcClientConsAppl
{
    class Program
    {
        static void Main(string[] args)
        {

            ConAp66.myserviceref.ServiceClient clientProxy = new ConAp66.myserviceref.ServiceClient();

            clientProxy.ClientCredentials.UserName.UserName = "xx";
            clientProxy.ClientCredentials.UserName.Password = "xx";

            clientProxy.Open();

            String ar1 = "xxx";
            String ar2 = "xxx";
            String ar3 = "xxx";
            ConAp66.myserviceref.eRes r = clientProxy.getRes1(ar1, ar2, ar3);

            clientProxy.Close();

            System.Console.ReadLine();
        }
    }
}

i get an error on line:
ConAp66.myserviceref.eRes r = clientProxy.getRes1(ar1, ar2, ar3);

saying that i have token authentication problems

any clues???
Your help would be greatly appreciated since i really don't know what to do...