I'm using D7 and I've found that menu disappears while it's linking to view with argument. Example:
I have a view called with it's path "/news" and it contains argument (Contextual Filter) "Has taxonomy term ID". So eg url like http://domain.com/news/5 should show me every node of news content type that is assign to term of tid 5. And it does but if I go to my menu settings and put it manually (path to menu item set to be news/5) as new menu item it disappears.
How to manage this thing?