i'm tring to browse an OpenLDAP server with (ASP) .NET 2.0 encrypted with TLS.

I followed
instructions and my code is:

using System.DirectoryServices.Protocols;

public string ldapAuth()
        {           

            string domainNameandPort = "ldap.server.com"; //i tested with ldap.server.com:389 
            string userName = "cn=user,ou=private_data,ou=performers,ou=applications,dc=server,dc=com";
            string password = "password";
            
            // establish a connection to the directory
            LdapConnection connection = new LdapConnection(domainNameandPort);

            NetworkCredential credential =
                new NetworkCredential(userName, password);

            connection.Credential = credential;
            connection.AuthType = AuthType.Basic;
            LdapSessionOptions options = connection.SessionOptions;
            
            options.ProtocolVersion = 3;
            options.SecureSocketLayer=false;
            string messages ="";

            try
            {
                  options.StartTransportLayerSecurity(null);
                messages += "TLS started.";
            }
            catch (Exception e)
            {
                messages += "Start TLS failed with " + e.Message;
                
            }

            try
            {
                connection.Bind();
                messages += "Bind succeeded using basic " +
                    "authentication and TLS.";

             }
            catch (LdapException e)
            {
                messages += e.Message;
            }

            try
            {
                options.StopTransportLayerSecurity();
                messages += "Stop TLS succeeded";
            }
            catch (Exception e)
            {
                messages +="Stop TLS failed with "+e.Message;
            }

            return messages;

        }

 I receive exceptions on StartTransportLayerSecurity(null) something like* "operation not allowed error"

 then i receive an exception "server not avaiable"

(* i have Italian framework,  don't know precise english diciture)

 
I tried Novell libraries too.. (and other that i don't mention)

i found only this  http://www.eggheadcafe.com/software/aspnet/31311857/systemdirectoryservices.aspx article, it seems my problem

Any suggestion?!