Index: engine.js
===================================================================
--- engine.js	(revision 2622)
+++ engine.js	(working copy)
@@ -1460,9 +1460,21 @@
         }
         var idname = dwr.engine.transport.iframe.getId(batch);
         batch.div = document.createElement("div");
+		if (!dwr.engine.isIE) {
+	        batch.iframe = document.createElement("iframe");
+	        batch.iframe.setAttribute("id", idname);
+	        batch.iframe.setAttribute("name", idname);
+	        batch.iframe.setAttribute("frameborder", "0");
+	        batch.iframe.src = "javascript:void(0)";
+	        batch.iframe.onload = "dwr.engine.transport.iframe.loadingComplete(" + batch.map.batchId + ");";
+	        batch.div.appendChild(batch.iframe);
+        }
         // Add the div to the document first, otherwise IE 6 will ignore onload handler.
         document.body.appendChild(batch.div);
-        batch.div.innerHTML = "<iframe src='javascript:void(0)' frameborder='0' style='width:0px;height:0px;border:0;' id='" + idname + "' name='" + idname + "' onload='dwr.engine.transport.iframe.loadingComplete(" + batch.map.batchId + ");'></iframe>";
+        if (dwr.engine.isIE) {
+        	batch.div.innerHTML = "<iframe src='javascript:void(0)' frameborder='0' style='width:0px;height:0px;border:0;' id='" + idname + "' name='" + idname + "' onload='dwr.engine.transport.iframe.loadingComplete(" + batch.map.batchId + ");'></iframe>";
+        	batch.iframe = batch.div.firstChild;
+        }
         batch.document = document;
         dwr.engine.transport.iframe.beginLoader(batch, idname);
       },
@@ -1482,7 +1494,6 @@
        * @param {Object} batch
        */
       beginLoader:function(batch, idname) {
-        batch.iframe = batch.document.getElementById(idname);
         batch.iframe.batch = batch;
         batch.mode = batch.isPoll ? dwr.engine._ModeHtmlPoll : dwr.engine._ModeHtmlCall;
         if (batch.isPoll) dwr.engine._outstandingIFrames.push(batch.iframe);
@@ -1502,8 +1513,8 @@
           batch.form = div.firstChild;
           for (var prop in batch.map) {
             var value = batch.map[prop];
-            if (value && typeof value != "function") {
-              if (value.tagName && value.tagName.toLowerCase() == "input" && value.type && value.type.toLowerCase() == "file") {
+            if (typeof value != "function") {
+              if (value && value.tagName && value.tagName.toLowerCase() == "input" && value.type && value.type.toLowerCase() == "file") {
                 // Since we can not set the value of a file object, we must post the actual file object
                 // that the user clicked browse on. We will put a clone in it's place.
                 var clone = value.cloneNode(true);
@@ -1513,10 +1524,10 @@
                 value.parentNode.removeChild(value);
                 batch.form.appendChild(value);
               } else {
-                var formInput = batch.document.createElement("input");
+				var formInput = batch.document.createElement("input");
                 formInput.setAttribute("type", "hidden");
                 formInput.setAttribute("name", prop);
-                formInput.setAttribute("value", value);
+                formInput.setAttribute("value", value == null ? "" : value);
                 batch.form.appendChild(formInput);
               }
             }