[Users] wfs Attributes using GeoExt.data.ProtocolProxy not shown up in Firefox

[Simon Appelt]

Hi list,
i'm new to GeoExt, so i started like some other guys with the GeoExt wfs 
example/tutorial published at OpenGeo.
So i want to displaing features in a grid,using 
GeoExt.data.ProtocolProxy, in IE the grid is filled with the Attributes 
from the topp:tasmania_water_bodies feature.
At Firefox nothing happens the grid is still empty and firebug says 
nothing (and ofc i deleted the ff cache). The Code i'm using is posted 
below.  Thanks, for any response!

<script type="text/javascript">
                Ext.BLANK_IMAGE_URL = "ext/resources/images/default/s.gif";

        Ext.onReady(function() {
             var store = new GeoExt.data.FeatureStore({
                 fields: [
                     {name: "WATER_TYPE", type: "string"},
                     {name: "CNTRY_NAME", type: "string"},
                     {name: "CONTINENT", type: "string"},
                     {name: "AREA", type: "int"}
                 ],
                 proxy: new GeoExt.data.ProtocolProxy({
                     protocol: new OpenLayers.Protocol.WFS({
                         url: "http://localhost:8080/geoserver/ows",
                         version: "1.1.0",
                         featureType: "tasmania_water_bodies",
                         featureNS: "http://www.openplans.org/topp",
                         srsName: "EPSG:4326"
                     })
                 }),
                 autoLoad: true
             });

             var gridPanel = new Ext.grid.GridPanel({
                 title: "Eingetragene Fl&auml;chen",
                 region: "center",
                 viewConfig: {forceFit: true},
                 store: store,
                 cm: new Ext.grid.ColumnModel({
                     defaults: {
                         sortable: true
                     },
                     columns: [
                         {header: "WATER_TYPE", dataIndex: "WATER_TYPE"},
                         {header: "CNTRY_NAME", dataIndex: "CNTRY_NAME"},
                         {header: "CONTINENT", dataIndex: "CONTINENT", 
width: 35},
                         {
                             xtype: "numbercolumn",
                             header: "Gr&ouml;sse",
                             dataIndex: "AREA",
                             format: "1,000",
                             align: "right",
                             width: 55
                         }
                     ]
                 })
             });

             var mainPanel = new Ext.Panel({
                 renderTo: document.body,
                 layout: "border",
                 height: 450,
                 width: 800,
                 items: [gridPanel]
             });
         });
</script>
Best regards,
Simon