Result Event = type was not found

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute">
	
	<mx:Script>
		<![CDATA[
			
			import flash.events.Event;
			
 			private function cepResult(event:ResultEvent):void{

				var resultXML:XMLList = new XMLList(new XML(event.result));
				if (resultXML != null && resultXML.retorno.resultado == 1){
					this.txtLogradouro.text = new String(resultXML.retorno.tipo_logradouro + " " + resultXML.retorno.logradouro);
					this.txtBairro.text = new String(resultXML.retorno.bairro);
					this.txtCidade.text = new String(resultXML.retorno.cidade);
					//this.comboUf.text = new String(resultXML.retorno.uf);
				}else{
					this.txtLogradouro.text = "";
					this.txtBairro.text = "";
					this.txtCidade.text = "";
					//this.comboUf.selectedIndex = 0;
					Alert.show("Cep não encontrado.", "Siart - Erro");
				}
		}	
		
		
		private function pesquisarCep(strCep:String):void{
			//Função que envia o cep para o web service e aguarda o endereço.
			if (strCep.length == 8){
				var url: String;
				url = "http:www.buscarcep.com.br/?formato=xml&cep=";
				buscaCep.url = "http:www.buscarcep.com.br/?formato=xml&cep=" + strCep;
				buscaCep.send();
			}
		}

	
			
		]]>
	</mx:Script>
	<mx:HTTPService id="buscaCep"  result="cepResult(event)" method="POST" showBusyCursor="true" resultFormat="e4x"/>
	<mx:Form width="100%" height="100%" horizontalCenter="0" verticalCenter="0">
		<mx:FormItem label="Label">
			<mx:TextInput id="txtLogradouro"/>
		</mx:FormItem>
		<mx:TextInput id="txtBairro"/>
		<mx:TextInput id="txtCidade"/>
		<mx:TextInput id="comboUf"/>
		<mx:FormItem label="cep">
			<mx:TextInput id="txtCep" />
		</mx:FormItem>
		<mx:FormItem label="ok" id="ok">
			<mx:Button label="Button" click="pesquisarCep(txtCep.text)"/>
		</mx:FormItem>


	</mx:Form>
	
</mx:Application>