Problem with deserialization of dynamically created ToolWind

  public partial class GroupPanel : ToolWindow, ITimerange, INotifiyTimerangeChanged
 {
. . . 
 }

 public class PanelLayout
 {
    private string _layout;

    [XmlAttribute()]
    public string Layout
    {
       get
       {
          return _layout;
       }
       set
       {
          _layout = value;
       }
    }
}

public partial class Dashboard : DocumentWindow, ITimerange, INotifiyTimerangeChanged
{
      public void Save()
      {
         XmlDocument xmlDasboard = new XmlDocument();

         XmlNode xmlDashboardNode = xmlDasboard.CreateElement("Dashboard");

         XmlAttribute attrDashboardName = xmlDasboard.CreateAttribute("Name");
         attrDashboardName.Value = this.Title;
         xmlDashboardNode.Attributes.Append(attrDashboardName);

         XmlAttribute attrDashboardVersion = xmlDasboard.CreateAttribute("Version");
         attrDashboardVersion.Value = "1.0";
         xmlDashboardNode.Attributes.Append(attrDashboardVersion);

         xmlDasboard.AppendChild(xmlDashboardNode);


         XmlNode xmlLayoutNode = xmlDasboard.CreateElement("Layout");

         if (_layoutSerializer == null)
         {
            _layoutSerializer = new DockSiteLayoutSerializer();
         }

         _layoutSerializer.CustomTypes.Add(typeof(PanelLayout));  // Register the custom data type
 _layoutSerializer.ObjectSerializedHandler = new EventHandler<ItemSerializationEventArgs>(OnObjectSerialized);

         xmlLayoutNode.InnerXml = _layoutSerializer.SaveToString(_dockSite);
         xmlDashboardNode.AppendChild(xmlLayoutNode);

         xmlDasboard.Save(@"c:\temp\dashboard.xml");
      }

public void Load()
{
         XmlDocument xmlDasboard = new XmlDocument();

         xmlDasboard.Load(@"c:\temp\dashboard.xml");

         XmlNode dashboard = xmlDasboard.SelectSingleNode("//Dashboard");

         string version = dashboard.Attributes["Version"].Value;

         if (version != "1.0")
         {
            return;
         }
    
         for (int n = _workspace.ToolWindows.Count - 1; n >= 0; n--)
         {
            ToolWindow window = _workspace.ToolWindows[n];
            window.Destroy();
         }

         Title = dashboard.Attributes["Name"].Value;

         XmlNode layout = xmlDasboard.SelectSingleNode("//Dashboard/Layout");

         if (_layoutSerializer == null)
         {
            _layoutSerializer = new DockSiteLayoutSerializer();
         }

         _layoutSerializer.CustomTypes.Add(typeof(PanelLayout));  // Register the custom data type
         _layoutSerializer.ObjectDeserializedHandler = new EventHandler<ItemSerializationEventArgs>(OnObjectDeserialized);
         _layoutSerializer.CanLoadToolWindowTitles = true;

         _layoutSerializer.LoadFromString(layout.InnerXml, _dockSite);

      }

      private void OnObjectSerialized(object sender, ItemSerializationEventArgs e)
      {
         if (e.Node is XmlDockSiteLayout)
         {
            
         }
         else if (e.Node is XmlToolWindow)
         {
            GroupPanel panel = e.Item as GroupPanel;
            PanelLayout layout = new PanelLayout();
            layout.Layout = panel.GetLayout();
            e.Node.Tag = layout;                        
         }
      }

      private void OnObjectDeserialized(object sender, ItemSerializationEventArgs e)
      {
         if (e.Node is XmlDockSiteLayout)
         {

         }
         else if (e.Node is XmlToolWindow)
         {
            <b>=> This code is never called!!!</b>            
            GroupPanel panel = new GroupPanel(this, _dockSite);
            PanelLayout layout = e.Node.Tag as PanelLayout;
            panel.RestoreLayout(layout.Layout);
         }
      }

}