title: Google Maps V3 Cluster will not reset after clearMarkers()
body: <p>I want to add and remove data sets from the clusterer - but when a particular data set cluster is toggled off the original (non-clustered) markers dont re-appear - i cant make them visible...</p>
  
  <pre><code>function clusterEvents(i)
  {
      cluster[0][i]=cluster[0][i]?0:1 // to tell which data set is in use
      if(cluster[1]) // clear the cluster
          cluster[1].clearMarkers()
      cluster[1]=new MarkerClusterer(map,[],{gridSize:50,maxZoom:15})
      for(i in iconz) // import markers
      {
          if(iconz[i].type&lt;20)
          {
              if(cluster[0][iconz[i].type]||cluster[0][iconz[i].type-6]) // if target then cluster
                  cluster[1].addMarker(iconz[i],true)
              else
                  **iconz[i].setVisible(true) // make it visible**
          }
      }
  }
  </code></pre>