This is a known problem that I discovered in the beta of the control.  The fix for it is to modify the dnnmenu.js file's selectNode method.
 
     if (mNode.selected)
     {
      var sJS = this.defaultJS;
      if (mNode.js.length > 0)
       sJS = mNode.js;
           
      if (sJS.length > 0)
      {
          this.update(true);  //always save state possible posting back (module actions)
       if (eval(sJS) == false)
        return; //don't do postback if returns false
      }
     
      if (mNode.clickAction == dnn.controls.action.postback)
      {
          this.update(true);  //always save state when posting back
       eval(this.postBack.replace('[NODEID]', mNode.id));
   }
      else if (mNode.clickAction == dnn.controls.action.nav)
       dnn.dom.navigate(mNode.getUrl(this), mNode.target.length > 0 ? mNode.target : this.target);
     }

Please note, that you will need to update the js/debug folder to easily read the file. Simply copy the file to the js folder when updated.

Hopefully I can release a new beta soon.