Issue with cluster strategy in OpenLayers

I have written the following code using Openlayers:

<script type="text/javascript">
    <!-- DEFINE PROXY.CGI URL -->
    OpenLayers.ProxyHost = "http://localhost/cgi-bin/proxy.cgi?url=";
    <!-- DEFINE GLOBAL VARIABLES -->
    var map,wms, control;
    <!-- DEFINE FUNCTION INIT -->
    function init(){
        map = new OpenLayers.Map('map',{}); // define map 
        wms = new OpenLayers.Layer.WMS( "OpenLayers WMS","http://ift.tt/PmQf9E", {layers: 'basic'} ); // define map layer

        strategy = new OpenLayers.Strategy.Cluster();

        <!-- OVERLAY WFS LAYER WITH KOMVUS FROM GEOSERVER -->
        wfs_layer_komvoi = new OpenLayers.Layer.Vector("Κόμβοι", {
            strategies: [strategy],
            protocol: new OpenLayers.Protocol.WFS({
                version: "1.1.0",
                url: "http://localhost:8080/geoserver/wfs", 
                featurePrefix: "rural", //workspace from geoserver
                featureType: "komvoipart", //layer name from geoserver
                featureNS : "http://ift.tt/1t6n1TB", //namespace from geoserver
                styles: "point"
            })
        })

        <!-- ADD LAYERS ETC -->
        map.addLayers([wms,wfs_layer_komvoi]);
        map.zoomToExtent( new OpenLayers.Bounds(36.190737, 35.353912,35.150577, 50.274810));



    } // end function init()

When I use as a strategy: Fixed the code gets some features from geoserver and displays them on the map without any problem. When I try to use a strategy: Cluster (as shown in the code) I get nothing back. I only see the map but no points. I checked for errors with firebug but there is nothing. Not even the POST request to the server.

What am I missing here???