HTTP/1.1 500 Internal Server Error when calling Web Service from .NET Client

Question

I'm trying to connect to a https web service (not .NET as far as I know). I can't control the other side in any way, I just got some standards and a wsdl to operate with it.

I have created at first the client using Add Service Reference, tried some things until I get through some problems, where one most serious was that I couldn't add the Authentication header to the message which was resulting in fail.

Added the service using old Add Web Reference and seemed more easily managed and appropriate, using a partial class and override the GetWebRequest, I added this code so I can preauthenticate with the service and add the security header, which they don't mention in the wsdl link. I know that it is not mandatory for services to tell this but it would be nice my Web Service creators fellow developers.

protected override WebRequest GetWebRequest(Uri uri)
{
    HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(uri);

    if (PreAuthenticate)
    {
        NetworkCredential networkCredentials = Credentials.GetCredential(uri, "Basic");
        if (networkCredentials != null)
        {
            byte[] credentialBuffer = new UTF8Encoding()
                .GetBytes(networkCredentials.UserName + ":" + networkCredentials.Password);

            request.Headers["Authorization"] = "Basic" + Convert.ToBase64String(credentialBuffer);
        }
        else
        {
            throw new ApplicationException("No network credentials");
        }
    }

    return request;
}

To call the service I added this code:

using (Service client = new Service()) // autogenerated Service class
        {
        client.EnableDecompression = true;

        // Create the network credentials and assign
        // them to the service credentials
        NetworkCredential netCredential = new                             NetworkCredential("test1", "test1");
        Uri uri = new Uri(client.Url);

        ICredentials credentials = netCredential.GetCredential(uri, "Basic");
        client.Credentials = credentials;

        // Be sure to set PreAuthenticate to true or else
        // authentication will not be sent.
        client.PreAuthenticate = true;

        // Make the web service call.

        Request req = new Request { UserName = "test2", Password = "test2"; // an object created from autogenerated code

        RequestResult result = client.processMessage(req); // autogenerated code

    }

While testing this call and checking with fiddler my request. I see 2 calls a keep alive call with these header, nothing special.

CONNECT server:443 HTTP/1.1
Host: server
Connection: Keep-Alive

Sending 570 returning a 200 result.

HTTP/1.1 200 Connection Established
FiddlerGateway: Direct
StartTime: 00:05:13.743
Connection: close

And the call with the data sending 571 result 500 error:

POST /host/Service HTTP/1.1
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; MS Web Services Client Protocol 2.0.50727.5448)
Authorization: BasicdXNlcOTc3MzQyMGTDFTR4dftfrdg5 // changed this hash for security reasons
VsDebuggerCausalityData: // Removed this hash for security reasons
Content-Type: text/xml; charset=utf-8
SOAPAction: ""
Host: server-host-url
Content-Length: 7238
Expect: 100-continue
Accept-Encoding: gzip
Connection: Keep-Alive

The error exception in .NET client:

Error on verifying message against security policy Error code:1000

As you see the Authorization header exist. I also tried with adding a space after Basic you can see above where exactly in the overriden method, and seemed fiddler recognized it better and also decoded the username:password header.

This results into that response:

HTTP/1.1 500 Internal Server Error
Date: Sat, 21 Apr 2012 21:05:22 GMT
Server: Oracle-Application-Server-11g
X-Powered-By: Servlet/2.5 JSP/2.1
X-Cnection: close
Transfer-Encoding: chunked
Content-Type: text/xml;charset="utf-8"
Content-Language: en
X-Pad: avoid browser bug
Set-Cookie: BIGipServerpoolXoas243_254_9999=437682499.99988.0000; path=/

The strange thing I wonder first is if the first call should be preauthenticated, the handshake keep alive one? This 500 error I know that causes when authentication header is not present, but mine is. Preauthentication is what I need to know how it should happen and I guess it's not working if it should appear in the 1st message.

Another strange thing is that if I change the 2 pairs of passwords opposite, I see on fiddler that I get 3 messages, 1 with the handshake and result in 200 and "TWO" others with 401 Authorization Required.

This drives me crazy. Any help appreciated to save my soul.

Thank you!