Single Sign-On of Windows-based Web Service Clients using SAP Logon Tickets

we run the following code..:

Imports System.Net
Imports System

Dim url As String = "http://hkbw3.pidpant.local:56100/irj/portal"
' Create a 'HttpWebRequest' object with the specified url.

Dim myHttpWebRequest As HttpWebRequest = CType(WebRequest.Create(url), httpWebRequest)
myHttpWebRequest.Credentials = CredentialCache.DefaultCredentials
myHttpWebRequest.CookieContainer = New CookieContainer()
Dim response As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)
response.Cookies = myHttpWebRequest.CookieContainer.GetCookies(myHttpWebRequest.RequestUri)
      
' Print the properties of each cookie.
Dim cook As Cookie
For Each cook In  response.Cookies
            Console.WriteLine("Cookie:")
            Console.WriteLine("{0} = {1}", cook.Name, cook.Value)
            Console.WriteLine("Domain: {0}", cook.Domain)
            Console.WriteLine("Path: {0}", cook.Path)
            Console.WriteLine("Port: {0}", cook.Port)
            Console.WriteLine("Secure: {0}", cook.Secure)
           
            Console.WriteLine("When issued: {0}", cook.TimeStamp)
            Console.WriteLine("Expires: {0} (expired? {1})", cook.Expires, cook.Expired)
            Console.WriteLine("Don't save: {0}", cook.Discard)
            Console.WriteLine("Comment: {0}", cook.Comment)
            Console.WriteLine("Uri for comments: {0}", cook.CommentUri)
            Console.WriteLine("Version: RFC {0}", IIf(cook.Version = 1, "2109", "2965"))
           
            ' Show the string representation of the cookie.
            Console.WriteLine("String: {0}", cook.ToString())
Next cook

At the line "Dim response As HttpWebResponse = CType(myHttpWebRequest.GetResponse(), HttpWebResponse)" the code fails, with an error '400'..

Browsing to the portal, however works fine, SSO works well, and a user is loged on with the Kerberos authentication ..

Looking into the logviewer we however see 2 entries..

The Second is successful: The first fails

Second entry >
Date : 06/22/2009
Time : 15:24:05:874
Message : LOGIN.OK
User: ldebock
Authentication Stack: ticket

Login Module                                                               Flag        Initialize  Login      Commit     Abort      Details
1. com.sap.security.core.server.jaas.EvaluateTicketLoginModule             SUFFICIENT  ok          exception  false                 java.security.SignatureException: Certificate (Issuer="CN=QP2", S/N=1393841314) not found.
2. com.sap.security.core.server.jaas.SPNegoLoginModule                     OPTIONAL    ok          true       true                 
3. com.sap.security.core.server.jaas.CreateTicketLoginModule               SUFFICIENT  ok          true       true                 
4. com.sap.engine.services.security.server.jaas.BasicPasswordLoginModule   REQUISITE   ok                     true                 
5. com.sap.security.core.server.jaas.CreateTicketLoginModule               REQUISITE   ok                     false                
Central Checks                                                                                                true                 
Severity : Info
Category : /System/Security/Authentication
Location : com.sap.engine.services.security.authentication.logincontext
Application : sap.com/irj
Thread : SAPEngine_Application_Thread[impl:3]_23
Datasource : 1245658549199:E:usrsapDP1JC52j2eeclusterserver0logsystemsecurity.log
Message ID : 00505689433600780000001E00000FA400046CEFC9D2828D
Source Name : /System/Security/Authentication
Argument Objs :
Arguments :
Dsr Component : n/a
Dsr Transaction : f5bf25205f2f11deb9ef005056894336
Dsr User :
Indent : 0
Level : 0
Message Code :
Message Type : 0
Relatives : com.sap.engine.services.security.authentication.logincontext
Resource Bundlename :
Session : 589
Source : /System/Security/Authentication
ThreadObject : SAPEngine_Application_Thread[impl:3]_23
Transaction :
User : ldebock

First Entry >

Date : 06/22/2009
Time : 15:24:05:327
Message : LOGIN.FAILED
User: N/A
Authentication Stack: ticket

Login Module                                                               Flag        Initialize  Login      Commit     Abort      Details
1. com.sap.security.core.server.jaas.EvaluateTicketLoginModule             SUFFICIENT  ok          exception             true       java.security.SignatureException: Certificate (Issuer="CN=QP2", S/N=1393841314) not found.
2. com.sap.security.core.server.jaas.SPNegoLoginModule                     OPTIONAL    ok          exception             true       Access Denied. No authorization header received.
3. com.sap.security.core.server.jaas.CreateTicketLoginModule               SUFFICIENT  ok          false                 true      
4. com.sap.engine.services.security.server.jaas.BasicPasswordLoginModule   REQUISITE   ok          false                 false     
5. com.sap.security.core.server.jaas.CreateTicketLoginModule               REQUISITE   ok          false                 true      
Severity : Info
Category : /System/Security/Authentication
Location : com.sap.engine.services.security.authentication.logincontext
Application : sap.com/irj
Thread : SAPEngine_Application_Thread[impl:3]_27
Datasource : 1245658549199:E:usrsapDP1JC52j2eeclusterserver0logsystemsecurity.log
Message ID : 00505689433600620000002A00000FA400046CEFC9CA4715
Source Name : /System/Security/Authentication
Argument Objs :
Arguments :
Dsr Component : n/a
Dsr Transaction : f56badf05f2f11de9745005056894336
Dsr User :
Indent : 0
Level : 0
Message Code :
Message Type : 0
Relatives : com.sap.engine.services.security.authentication.logincontext
Resource Bundlename :
Session : 0
Source : /System/Security/Authentication
ThreadObject : SAPEngine_Application_Thread[impl:3]_27
Transaction :
User : Guest

When trying to acquire a ticket through VB-code, only one entry appears .. The faulty one..

What needs to be done in the codeing ?
Any advice ?