After upgrading to WP 3.6 The submenu items in my WordPress generated Navigation Menu stopped working. You can see how they work at BarTaste.com. I disabled all plugins and reactivated them one by one. It turns out it is the jQuery Vertical Mega Menu plugin which is causing this. I had several JQuery Vertical Mega Menu items in my left sidebar but disabled them because it breaks the primary navigation menu of my site. Suggestions are appreciated.