Try to use XMLHttpRequest in more cases in IE 7. Thanks to Matt Kruse and Sam...

Try to use XMLHttpRequest in more cases in IE 7. Thanks to Matt Kruse and Sam Collett for the suggestions. Fixes #3623, #2849, #5338, and #5529.

src/ajax.js

@@ -175,12 +175,13 @@ jQuery.extend({
 		traditional: false,
 		*/
 		// Create the request object; Microsoft failed to properly
-		// implement the XMLHttpRequest in IE7, so we use the ActiveXObject when it is available
+		// implement the XMLHttpRequest in IE7 (can't request local files),
+		// so we use the ActiveXObject when it is available
 		// This function can be overriden by calling jQuery.ajaxSetup
 		xhr: function() {
-			return window.ActiveXObject ?
-				new ActiveXObject("Microsoft.XMLHTTP") :
-				new XMLHttpRequest();
+			return window.XMLHttpRequest && window.location.protocol !== "file:" || window.ActiveXObject ?
+				new window.XMLHttpRequest() :
+				new window.ActiveXObject("Microsoft.XMLHTTP");
 		},
 		accepts: {
 			xml: "application/xml, text/xml",