CustomMenu Name and Category Name Conflict

I try to create a custom menu for each of my categories (to show subcategories) and that menu will have the exact same name as the category name. The weird thing that happened is that when I changed the name of the custom menu, the name of the category also changed and the permalink of that category changed as well and so I get a 404 error page when I try to open the category page. Is it just me or is this a bug or am I doing something wrong here? I tried it on 2 different WP installations and both showed the same behavior.

Any ideas?