GetFeatureInfo Request with GeoServer and OpenLayers.loadURL Not Working

I'm making a simple GetFeatureInfo request against a GeoServer WMS, but it returns empty responses. The request utility I'm using is OpenLayers.loadURL.

The funny thing is, I can paste the generated request URL from FireBug into a new browser tab and get a valid response. So, it seems to be something with the OpenLayers.loadURL. See the examples below.

I can get a valid response with this map event where the GetFeatureInfo request is in a new window:

  map.events.register('click', map, function (e) {
    var url = "http://localhost:8080/geoserver/MYLAYER/wms" 
    var params = "" 

      + "REQUEST=GetFeatureInfo"
      + "&SERVICE=WMS"
      + "&EXCEPTIONS=application/vnd.ogc.se_xml"
      + "&VERSION=1.1.1"
      + "&BBOX=" + map.getExtent().toBBOX()
      + "&X=" + Math.round(e.xy.x)
      + "&Y=" + Math.round(e.xy.y)
      + "&INFO_FORMAT=text/html"
      + "&QUERY_LAYERS=NERD:NERD Risk Rates"
      + "&LAYERS=NERD:NERD Risk Rates"

      + "&FEATURE_COUNT=50"
      + "&format=image/png"
      + "&SRS=EPSG:900913"
      + "&STYLES="
      + "&WIDTH=" + map.size.w
      + "&HEIGHT=" + map.size.h;

    console.log(url+"?"+params);
    window.open(url+"?"+params,
      "getfeatureinfo",

      "location=0,status=0,scrollbars=1,width=600,height=150"
    );

   });

However, this map event using OpenLayers.loadURL always returns an empty response and no error. But if I cut and paste the GET request url from FireBug into a new browser window, I get the proper response:

  map.events.register('click', map, function (e) {
    var url = "http://localhost:8080/geoserver/MYLAYER/wms" 

    var paramHash =  {

      REQUEST : "GetFeatureInfo" ,
      EXCEPTIONS : "application/vnd.ogc.se_xml" ,
      SERVICE : "WMS" , 
      VERSION : "1.1.1" ,
      BBOX : map.getExtent().toBBOX() ,
      X : Math.round(e.xy.x) ,
      Y : Math.round(e.xy.y) ,
      INFO_FORMAT : "text/html" , 
      QUERY_LAYERS : "NERD:NERD Risk Rates" , 
      LAYERS : "NERD:NERD Risk Rates" ,

      FEATURE_COUNT : 50 , 
      format : "image/png" ,
      srs : "EPSG:900913" ,
      styles : "" ,
      WIDTH : map.size.w , 
      HEIGHT : map.size.h
    };

    OpenLayers.loadURL(url, paramHash, this, setHTML, setHTML);
        OpenLayers.Event.stop(e);


   });

Someone have any ideas?

Answer

Sounds like a same origin problem to me. Are you serving your page from a different host/port combination than the map server? See http://trac.osgeo.org/openlayers/wiki/FrequentlyAskedQuestions#ProxyHost for details of how to fix this using a proxy or move your html page to data/web in your geoserver installation.