String passed to URLVariables.decode() must be a URL-encoded query string

1

I really don’t understand why this won’t work? I’ve made a test which sends some POST data to a script on my page which works fine. But why does not this work?

            var mapsize = _cmap.fieldx.toString(16) + _cmap.fieldy.toString(16);
            var names = "Zomis_AI6";
            var description = "descr";
            var result = "gameresult";
            var upldata: String = "mapsize="+mapsize+"&names="+names+"&description="+description+"&result="+result;
            trace(upldata);
            var variables:URLVariables = new URLVariables(upldata);
            var request2:URLRequest = new URLRequest();
            request2.url = "http://www.zomis.net/record.php";
            request2.method = URLRequestMethod.POST;
            request2.data = variables;
            var loader2:URLLoader = new URLLoader();
            loader2.dataFormat = URLLoaderDataFormat.VARIABLES;
            loader2.addEventListener(Event.COMPLETE, uploadcomplete);
            try    {
                loader2.load(request2);
                trace("Loaded");
            }
            catch (error:Error)    {
                trace("Unable to load URL");
            }

Tracing gets:

mapsize=1010&names=Zomis_AI6&description=descr&result=gameresult
Loaded
Error: Error #2101: The String passed to URLVariables.decode() must be a URL-encoded query string containing name/value pairs.
    at Error$/throwError()
    at flash.net::URLVariables/decode()
    at flash.net::URLVariables$iinit()
    at flash.net::URLLoader/flash.net:URLLoader::onComplete()