error call the GP Server in flex 4.6

yanli

<fx:Declarations>
<esri:Geoprocessor  executeComplete="gp_jobCompleteHandler(event)"  useAMF="false"  showBusyCursor="true"     id="gp"        url="http://yanli/arcgis/rest/services/gp1/GPServer/polygon"/>

</fx:Declarations>
gp.execute(param);  //  error  here!!!

when  i  chang the  code  with  setting  "URL" null  ??the  error  is  same .... but  the param  have  the  value,the GP server run  well  in the ArcMAP

<fx:Declarations>
<esri:Geoprocessor  executeComplete="gp_jobCompleteHandler(event)"  useAMF="false"  showBusyCursor="true"     id="gp"        url=""/>

</fx:Declarations>
gp.execute(param);  //  error  here!!!

I  am  carazing    !!!!!!!!!!!!!!!now

the error  message  as following:

TypeError: Error #1009:Can not access a property or method of a null object reference???
at com.esri.ags.utils::GeometryUtil$/http://www.esri.com/2008/ags/internal::normalizeCentralMeridian2()
at com.esri.ags.utils::GeometryUtil$/normalizeCentralMeridian()
at com.esri.ags.tasks::Geoprocessor/toURLVariables()
at com.esri.ags.tasks::Geoprocessor/execute()
at test2/onQueryResult()
at mx.rpc::AsyncResponder/result()
at com.esri.ags.tasks::QueryTask/handleExecute()
at Function/http://adobe.com/AS3/2006/builtin::call()
at com.esri.ags.tasks::BaseTask/loaderCompleteHandler()
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at flash.net::URLLoader/onComplete()

Anonymous User

Other troubleshooting steps would be to test your GP service using its REST page. If the service gives you the expected results back, it should work in your flex code.  Other things to check would be what gets sent in the http request. You can use firebug here to help. Copy the FeatureSet JSON representation and then test it using your REST page.  Also make sure your GP service is synchronous, as I see you are using execute vs submitJob.