Filter function causing 0 items in combo box

Question

HI there, I have combobox with the dataProvider set up like below
    <mx:ComboBox rowCount="10" id="selectUser" 
                    dataProvider="{VO.getInstance().clientsResultForAddTrade}" width="258"
                    x="28" y="10" >        
                </mx:ComboBox>
in the VO class I have some code that calls the filter function (when clientsResultForAddTrade is refreshed in the clientsDataChangeHandler) when the clientsResultForAddTrade data changes.
      private function clientsDataChangeHandler( event:PropertyChangeEvent ):void{
           clientsResultForAddTrade.refresh();
        public function VO(caller:Function=null)
            if (caller != VO.getInstance)
                throw new Error("Singleton is a singleton class, use getInstance() instead");
            if (VO.instance != null)
                throw new Error("Only one Singleton instance should be instantiated");
            //put instantiation code here
            clientsResultForAddTrade.filterFunction = clientAuthorisedFilterFunction;
             activityWatcher = ChangeWatcher.watch( this, "clientsResultForAddTrade", clientsDataChangeHandler);
            private function clientAuthorisedFilterFunction(item:Object):Boolean
                var b:Boolean =  item.status == 'Authorised';
                return item.status == 'Authorised';
However there are 0 items in the selectUser combobox after the filter function is called, I have checked that it returns true when item.status == 'Authorised'
Please advise, 10 points available

Answer 1

Could it be a problem with the way I assign the data in the first place?
private function handleGetClients(event:ResultEvent):void
                VO.getInstance().clientsResult=event.result as ArrayCollection;
                //the following has a filter function in the model that automaticly refreshes
                VO.getInstance().clientsResultForAddTrade.source = (event.result as ArrayCollection).source;