Call to NAV Web Service from Classic works from RTC don't

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Please Help I'm Desperate!
I've done some coding in the classic to call a NAV 2009 codeunit function exposed as web service...

  XmlHttp.open('POST','http://localhost:7047/' + NAVServerName + '/ws/' + Company.Name + '/Codeunit/' +
               WebService."Service Name",0);

  XmlHttp.setRequestHeader('Content-Type','text/xml; charset=utf-8');
  XmlHttp.setRequestHeader('SOAPAction','ConvertWAMPS2Vendor');

  //The last parameter set to zero allows to wait till webservice finishes
  XmlHttp.setTimeouts(10000,10000,10000,0);

  XmlHttp.send('<?xml version="1.0" encoding="utf-8"?>' + 
               '<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">' +
               '<soap:Body><ConvertWAMPS2Vendor xmlns="urn:microsoft-dynamics-schemas/codeunit/' +
               WebService."Service Name" + '">' +
               '</ConvertWAMPS2Vendor></soap:Body></soap:Envelope>');

  XmlDoc.async := FALSE;
  XmlDoc.load(XmlHttp.responseBody);

  XmlDoc.save('C:\' + Company.Name + 'testwebresponse.xml');

  IF XmlHttp.status <> 200 THEN BEGIN

    XmlNode := XmlDoc.selectSingleNode(ErrorDetailPath);

    IF NOT ISCLEAR(XmlNode) THEN
      MESSAGE(Company.Name + ': ' + XmlNode.text)
    ELSE
      MESSAGE(Company.Name + ' Http Error ' + ' ' + FORMAT(XmlHttp.status) + ': ' + XmlHttp.statusText);

  END ELSE BEGIN

    //ALL OK

  END;

This works fine if I try to call it from the Classic Client but when instead I call it from the RTC I have this message:

- <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"&gt;
- <s:Body>
- <s:Fault>
<faultcode xmlns:a="urn:microsoft-dynamics-schemas/error">a:Microsoft.Dynamics.Nav.Types.NavDatabasePasswordException</faultcode>
<faultstring xml:lang="en-GB">The user ID and password are invalid. Try again.</faultstring>
- <detail>
<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">The user ID and password are invalid. Try again.</string>
</detail>
</s:Fault>
</s:Body>
</s:Envelope>

Why is doing that?
I don't understand please help me to solve and understand why!!!!

THANKS!