[Chateau Theme] – WP Nav Menu Dissapears in Category Pages!

Hello, My categories in the submenu bar when clicked, the main navi disappears. This only happens on categories…I saw this website but I have no idea where or how to add code or how to add a template. If anybody can walk me through this I’d greatly appreciate it. I found the discussion here : http://wordpress.org/support/topic/wp-nav-menu-dissapears-in-category-pages-1

My website is exercisingcap.com