diff --git a/lib/OpenLayers/Util.js b/lib/OpenLayers/Util.js
index 0eb4de6c69..8daaaea6f4 100644
--- a/lib/OpenLayers/Util.js
+++ b/lib/OpenLayers/Util.js
@@ -56,12 +56,24 @@ OpenLayers.Util.extend = function(destination, source) {
                 destination[property] = value;
             }
         }
+
         /**
          * IE doesn't include the toString property when iterating over an object's
          * properties with the for(property in object) syntax.  Explicitly check if
          * the source has its own toString property.
          */
-        if(source.hasOwnProperty && source.hasOwnProperty('toString')) {
+
+        /*
+         * FF/Windows < 2.0.0.13 reports "Illegal operation on WrappedNative
+         * prototype object" when calling hawOwnProperty if the source object
+         * is an instance of window.Event.
+         */
+
+        var sourceIsEvt = typeof window.Event == "function"
+                          && source instanceof window.Event;
+
+        if(!sourceIsEvt
+           && source.hasOwnProperty && source.hasOwnProperty('toString')) {
             destination.toString = source.toString;
         }
     }
@@ -510,9 +522,18 @@ OpenLayers.Util.upperCaseObject = function (object) {
  *     in place and returned by this function.
  */
 OpenLayers.Util.applyDefaults = function (to, from) {
+
+    /*
+     * FF/Windows < 2.0.0.13 reports "Illegal operation on WrappedNative
+     * prototype object" when calling hawOwnProperty if the source object is an
+     * instance of window.Event.
+     */
+    var fromIsEvt = typeof window.Event == "function"
+                    && from instanceof window.Event;
+
     for (var key in from) {
         if (to[key] === undefined ||
-            (from.hasOwnProperty
+            (!fromIsEvt && from.hasOwnProperty
              && from.hasOwnProperty(key) && !to.hasOwnProperty(key))) {
             to[key] = from[key];
         }
@@ -522,7 +543,7 @@ OpenLayers.Util.applyDefaults = function (to, from) {
      * properties with the for(property in object) syntax.  Explicitly check if
      * the source has its own toString property.
      */
-    if(from.hasOwnProperty
+    if(!fromIsEvt && from.hasOwnProperty
        && from.hasOwnProperty('toString') && !to.hasOwnProperty('toString')) {
         to.toString = from.toString;
     }