Index: ajax.js
===================================================================
--- ajax.js	(revision 6484)
+++ ajax.js	(working copy)
@@ -543,7 +543,14 @@
 		var ct = xhr.getResponseHeader("content-type"),
 			xml = type === "xml" || !type && ct && ct.indexOf("xml") >= 0,
 			data = xml ? xhr.responseXML : xhr.responseText;
-
+		
+		// IE 6 & 7 fail to recognise Content-Types ending +xml (eg application/rss+xml)
+		// as XML, so we create an XML object from the text here
+		if (xml && jQuery.browser.ie && /\+xml$/.test(ct)) {
+			data = new ActiveXObject("Microsoft.XMLDOM");
+			data.loadXML( xhr.responseText );
+		}
+		
 		if ( xml && data.documentElement.nodeName === "parsererror" ) {
 			throw "parsererror";
 		}