Index: api/src/main/javascript/META-INF/resources/myfaces/_impl/xhrCore/_AjaxResponse.js
===================================================================
--- api/src/main/javascript/META-INF/resources/myfaces/_impl/xhrCore/_AjaxResponse.js	(revision 1352685)
+++ api/src/main/javascript/META-INF/resources/myfaces/_impl/xhrCore/_AjaxResponse.js	(working copy)
@@ -203,7 +203,18 @@
 
         if (!theForm) return;
 
-        var viewStateField = (theForm.elements) ? theForm.elements[this.P_VIEWSTATE] : null;//this._Dom.findFormElement(elem, this.P_VIEWSTATE);
+        //in IE7 looking up form elements with complex names (such as 'javax.faces.ViewState') fails in certain cases
+        //iterate through the form elements to find the element, instead
+        var viewStateField = null;
+        if (theForm.elements) {
+            var elements = theForm.elements;
+            for (var i = 0, l = elements.length; i < l; i++) {
+                var e = elements[i];
+                if (e.name == this.P_VIEWSTATE) {
+                    viewStateField = e;
+                }
+            }
+        }
 
         if (viewStateField) {
             this._Dom.setAttribute(viewStateField, "value", mfInternal.appliedViewState);