title: Marker Manager not showing markers
body: <p>I am having problems using the MarkerManager. Somehow Markers added with the MarkerManager do not show up, though i do <code>mgr.refresh();</code> It works when i use basic <code>map.addOverlay(marker);</code> but not when using <code>mgr.addMarker(marker);</code>. Weird. Hope someone here can help.</p>
  
  <p>Here's the relevant code:</p>
  
  <pre><code>  if (GBrowserIsCompatible()) {
      map = new GMap2(document.getElementById("map"));
      bounds = new GLatLngBounds();
      map.setCenter(new GLatLng(48.25, 11.00), 4);
  
      mgr = new MarkerManager(map, mgr_options);
      markers = createSpotMarkers(spots); // parsing spots, extending bounds, creating Array of GMarkers etc, pretty basic and seems not be relevant.
      mgr.addMarkers(markers); // does not work
      map.addOverlay(markers[0]); // works
      mgr.addMarker(markers[0]); // does not work either 
  
      map.setCenter(bounds.getCenter(), map.getBoundsZoomLevel(bounds)-1);
      mgr.refresh();
    } 
  </code></pre>