Loaded XML File Failing Due To Doctype Tag

I have an XML file that I'm trying to load into and xml object, however the doctype tag is killing the javascript, and does not parse the XML at all. If I remove the doctype, the javascript can parse, and I can access the XML DOM. So I know the XML is valid. Even with the Doctype, it validates. However Javascript does not like it. I don't have a choice to remove the Doctype tag of the XML.

If I remove the Doctype, this method works to parse the XML DOM:
Code:
xmlDoc = new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async = false;
xmlDoc.load(filename);

Also, if I use the .open method to retrieve the XML, I cannot access the XML DOM via xmlhttp.responseXML. But I do get a result when I use xmlhttp.responseText, it displays the corresponding XML.
Code:
xmlhttp.open("GET", filename, false);