I had the same problem on a DNN6.0 site. The code was slightly different in the menu.js file, I added the same additional code and it seems to have fixed the problem.

this._hideMenusDelegate=dnn.createDelegate(this,this.hideMenus);this._expandNodeDelegate=dnn.createDelegate(this,this.__expandNode);},generateMenuHTML:function()
{this.container.className=this.mbcss;dnn.dom.disableTextSelect(this.container);
if(this.rootNode!==null){for(var i=0;i<this.rootNode.childNodeCount();i++)this.renderNode(this.rootNode.childNodes(i),this.container);this.addHandlers(document.body,{"click":this._bodyClick},this);}if(dnn.dom.browser.isType(dnn.dom.browser.Mozilla,dnn.dom.browser.Safari)==false)dnn.setVar(this.ns + '_json', '');},renderNode:function(node,ctr)
{var mNode=new dnn.controls.DNNMenuNode(node);if(mNode.selected)
this.selMNode=mNode;var menuBuilder=this._getMenuBuilder(mNode,ctr);if(menuBuilder.alreadyRendered==false)


I am not a JS developer so if anyone can see a problem with my change I would appreciate feedback.

 Thanks a lot Kevin.

I had that issue in about 30 portals and it will be very difficult change the menu in every skin.

I did that and my problem seems to be solved.

Thanks again

Regards

I had problem with multiple copies of menu on a newly installed 5.6.3. Downloaded 6.0.1 and copied dnn.controls.dnnmenu.js from the zip file. Problem gone!