       @on 'change:presentList', @calculate
       log '@ Object MasterControl created.', DEBUG
     register: (v, n, c) ->
-      @get('threadStack').push @get('ongoing')
-      appView.unrender  @get('ongoing').cls
+      old = @get('ongoing')
+      @get('threadStack').push old
+      appView.unrender old
+      old.view.undelegateEvents()
+
       @set 'ongoing',
         view: v
         name: n

      super("Moderacted Caucus", 'mc-view')
      log '\t$ MCView initialized.', DEBUG
    render: ->
      super()
      h  = "<div class=\"mc-title\">Topic: #{@params.topic}</div>"
      h += '<hr>'
      @$el.prepend h
      h  = '<hr>'
      h += '<button class="btn btn-info" id="btn-exit-umc">Close this Moderated Caucus</button>'
      @$el.append h
      @

  class UMCView extends Backbone.View

    unregister: (c) ->
      return @  if @get('ongoing').cls != c or c == 'idle'
      appView.unrender(c)
      # get the last view back
      last = @get('threadStack').pop()
      @set 'ongoing',
        view: last.view
        name: last.name
        cls: last.cls
      last.view.render()
      last.view.delegateEvents()
      @logStack true, c
      @
    calculate: ->
