WCF and x509 certificates

Hope you can help me with this. I am fairly new to WCF and created a WCF service and a client, both working fine when on the same server and same website (win2003/iis6). Now I wanted to host WCF services on a separate machine. I created a test environment with two Win2003/IIS6 servers. One hosts WCF services, another one hosts the website that consumes those services. I set up x509 certificates as per this article: http://www.codeproject.com/KB/WCF/wcf_certificates.aspx

I ran into a bunch of errors which I resolved and now I am stuck on this error for few days already:

The request for security token has invalid or malformed elements.

Here's the client code:

        WCFCategories.CategoriesClient client = new WCFCategories.CategoriesClient();
        Textbox1.Text = client.GetCategoriesInXML(611);


Here are my service / client web.config files:

SERVICE
--------------------



   
     
                  address="http://s.foo.com:8228/Services/Categories.svc"
          binding="wsHttpBinding"
          contract="ICategories"/>
                  address="mex"
          binding="mexHttpBinding"
          contract="IMetadataExchange"/>
     
   

   
     
       
         
           
         
       
     
       
   
   
           
               
                   
         
                   
                       
                                            certificateValidationMode="ChainTrust"
                revocationMode="NoCheck"/>
                       
                                      findValue="My Server Machine"
              x509FindType="FindBySubjectName"
              storeLocation="LocalMachine"
              storeName="My"/>
                   
               
           
       


   

CLIENT
----------------------------
 
 
   
              address="http://s.foo.com:8228/Services/Categories.svc"
        behaviorConfiguration="customBehavior"
        binding="wsHttpBinding"
        bindingConfiguration="customWsHttpBinding"
        contract="WCFCategories.ICategories"
        name="WSHttpBinding_ICategories">
       
         
       
     
   
   
   
     
       
         
                           x509FindType="FindBySubjectName"
               findValue="My Client Machine"
               storeLocation="LocalMachine"
               storeName="My"/>
           
                              certificateValidationMode="ChainTrust"
                revocationMode="NoCheck"/>