Flex 发送数据出错

[RPC Fault faultString="HTTP request error" faultCode="Server.Error.Request" faultDetail="Error: [IOErrorEvent type="ioError" bubbles=false cancelable=false eventPhase=2 text="Error #2032: 流错误。 URL: http://localhost:8080/vbm/videoTrackHist/videoTrackAdd.htm"]. URL: http://localhost:8080/vbm/videoTrackHist/videoTrackAdd.htm"]
    at mx.rpc::AbstractInvoker/http://www.adobe.com/2006/flex/mx/internal::faultHandler()[C:"autobuild"3.2.0"frameworks"projects"rpc"src"mx"rpc"AbstractInvoker.as:220]
    at mx.rpc::Responder/fault()[C:"autobuild"3.2.0"frameworks"projects"rpc"src"mx"rpc"Responder.as:53]
    at mx.rpc::AsyncRequest/fault()[C:"autobuild"3.2.0"frameworks"projects"rpc"src"mx"rpc"AsyncRequest.as:103]
    at DirectHTTPMessageResponder/errorHandler()[C:"autobuild"3.2.0"frameworks"projects"rpc"src"mx"messaging"channels"DirectHTTPChannel.as:362]
    at flash.events::EventDispatcher/dispatchEventFunction()
    at flash.events::EventDispatcher/dispatchEvent()
    at flash.net::URLLoader/onComplete()

当本地服务器关闭时，没有成功错误响应的时候flex builder报错如上

代码:  
    var param:URLVariables = new URLVariables();
    param.query = query;
   
    var v:HTTPService = new HTTPService;
    v.method = URLRequestMethod.POST;
    //v.method = 'POST';
    v.resultFormat="text";
    v.url = url ;
    v.send(param);