if(Ext.isIE) {
        function fnCleanUp() {
            var p = Function.prototype;
            delete p.createSequence;
            delete p.defer;
            delete p.createDelegate;
            delete p.createCallback;
            delete p.createInterceptor;

            window.detachEvent("onunload", fnCleanUp);
        }
        window.attachEvent("onunload", fnCleanUp);
    }
})();