I am developing a VB.NET Client accesses a web service via the following 
code:

Imports System
Imports System.Diagnostics
Imports System.Net
Imports System.Security
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Xml.Serialization

' Proxy class
<System.Web.Services.WebServiceBindingAttribute( _
 Name:="soapClient", _
 [Namespace]:="urn:soapClient")> _
Public Class soapClient
    Inherits System.Web.Services.Protocols.SoapHttpClientProtocol

    ' Hard-code userid and password - for testing
    Dim myCred As New NetworkCredential("user", "passwd")
    Dim myCache As New CredentialCache()

    ' Constructor: pass in user/app userid and passwd when creating new 
soapClient
    <System.Diagnostics.DebuggerStepThroughAttribute()> _
    Public Sub New()
        MyBase.New()
        ' HTTPS
        Me.Url = "https://"

        ' HTTP
        'Me.Url = "http://"

        myCache.Add(New Uri("https://"), "Basic", myCred)
        'myCache.Add(New Uri("http://"), "Basic", myCred)

        Me.Credentials = myCache
    End Sub

    ' Web service
    <System.Diagnostics.DebuggerStepThroughAttribute(), _
    System.Web.Services.Protocols.SoapDocumentMethodAttribute( _
     "urn:soapClient/echo", _
     RequestNamespace:="urn:Echo", _
     ResponseNamespace:="urn:soapClient", _
     Use:=System.Web.Services.Description.SoapBindingUse.Encoded, _
     ParameterStyle:= _
      System.Web.Services.Protocols.SoapParameterStyle.Wrapped)> _
    Public Function echo(ByVal Name As String) As String
        Dim results() As Object = Me.Invoke("echo", New Object() {Name})
        Return CType(results(0), String)
    End Function

End Class

I have left out the URI on purpose. I can access the method over HTTP with 
and without authentication. I can also access the method over HTTPS 
without authentication, but when I try to access the method with 
authentication over HTTPS I get the following error message:

 An unhandled exception of type 'System.Net.WebException' occurred in 
system.web.services.dll

Additional information: The underlying connection was closed: The server 
committed an HTTP protocol violation.

I checked the server and it is throwing a SocketException: Socket Closed. 
It looks like the client sends a request twice; first without the 
password, and then with the userid and the password.

Does anybody have an idea on how to resolve this? Any help would be 
greatly appreciated.

Thanks,

Toby