在JS中调用AS的函数出问题

通过JS调用AS中的函数，进行POST操作时，到提交请求那一步就停了。如下代码，loader.load(request);前一句还能正常执行，下一步就没有反应了，没有POST请求，也没有错误。
而直接在AS中调用这个函数，就可以正常提交。

Chrome中有如下错误，但是感觉不是这里的问题，别的浏览器没有错误。

Uncaught TypeError: Cannot use 'in' operator to search for 'rawScopes' in undefined

JS调用与AS调用有啥区别吗？
已经设置 <param name="allowScriptAccess" value="always">

public function saveFileToServer(data:ByteArray, filename:String, whenDone:Function):void {
        var values:URLVariables = new URLVariables();
        values.key = "Message";

        var header:URLRequestHeader = new URLRequestHeader("pragma", "no-cache");
        var request:URLRequest = new URLRequest("/save");
        var data = getData();// function to get data to post

        request.contentType = "multipart/form-data; boundary=" + UploadPostHelper.getBoundary();
        request.requestHeaders.push(header);
        request.method = URLRequestMethod.POST;
        request.data = UploadPostHelper.getPostDataMultiFiles(
            {
                data:data
            } );

        var loader:URLLoader = new URLLoader();
        loader.dataFormat = URLLoaderDataFormat.BINARY;
        loader.addEventListener(Event.COMPLETE, whenDone);
        loader.addEventListener(SecurityErrorEvent.SECURITY_ERROR,function(err:ErrorEvent):void
        {
            Scratch.app.logMessage("Failed server request for ");
            ExternalInterface.call("console.log", "SECURITY_ERROR");
        });
        loader.addEventListener(IOErrorEvent.IO_ERROR,function(err:ErrorEvent):void
        {
            Scratch.app.logMessage("Failed server request for ");
            ExternalInterface.call("console.log", "IO_ERROR");
        });
        loader.addEventListener(ProgressEvent.PROGRESS,function(event:ProgressEvent):void
        {
            ExternalInterface.call("console.log", "PROGRESS");
        });
        try {
            ExternalInterface.call("console.log", "Before load");  //this is line is logged successfully.
            loader.load(request);
        }
        catch (error:ArgumentError) {
            trace("An ArgumentError has occurred."); // no error caught.
        }
        catch (error:SecurityError) {
            trace("A SecurityError has occurred.");
        }catch (error:*){
            trace("other errors");
        }
    }

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var request:URLRequest = new URLRequest("/save");这里的地址改成绝对地址试试