Calling webservice with NTLM authentication and getting error 'System.CalloutException: Web service callout failed: Unexpected element. Parser was expecting element 'http://schemas.xmlsoap.org/soap/envelope/:Envelope' but found ':HTML'' I am able to access the webservice through browser but not through apex.
Perhaps the authentication is failing and the page is returning HTML as an "error" page.
Update your question with more details - how did you upload your WSDL? Have you used SoapUI to test your callouts and review the results?
This is what I do before I try to debug my SOAP callouts on the Salesforce APEX environment.