title: The content type text/html; charset=utf-8 of the response message does not match the content type of the binding
body: <p>I am maintaining a large project that uses a lot of WCF services and when certain users log in to the site they get this error</p>
  
  <pre><code>The content type text/html; charset=utf-8 of the response message does not match the content type of the binding (application/soap+xml; charset=utf-8). If using a custom encoder, be sure that the IsContentTypeSupported method is implemented properly. The first 1024 bytes of the response were: ' '.
  </code></pre>
  
  <p>I don't know what the cause of this could be, nor where to look to fix it.  Any ideas?</p>