Menu Disappear when adding various links to the menu

I run a holiday accommodation website.

To simply the navigation I wanted to add a menu under each suburb showing the number of people various homes in that suburb can sleep.

Categories list the suburb and tags the number it can sleep. I can then create various links as follows http://capeholidays.info/category/atlantic-seaboard-homes/camps-bay/?tag=%22sleeps-12%22

As soon as I add these links (as links at the menu interface), after adding a couple the whole main menu disappears and only shows up again after I have removed these link menu items from the menu.

Any idea what the cause may be or if you have another solution please let me know?
Regards