An old trick, but I'd thought I'd write it down anyway... You can configure Firefox to automatically send NTLM credentials without prompting for certain web sites by setting the about:config property network.automatic-ntlm-auth.trusted-uris to a comma-separated list of host names.
If your XML document uses the Windows character set, you must set the encoding of the XML document to "ISO-8859-1". Otherwise, some XML processors (like Internet Explorer) will complain about an invalid character. A particularly common case of non-ASCII characters in an otherwise normal file occurs when the text was generated in Microsoft Word and included quote characters that had been converted into "smart quotes".