This is my custom post type:
https://www.dropbox.com/s/mwk5pyulru1b8qr/Screenshot%202014-07-31%2008.45.11.png
But in ACF the label is hidden:
https://www.dropbox.com/s/saa0fyp7k5og634/Screenshot%202014-07-31%2008.45.57.png
as you can see i can select it but it is somehow complicated ;-).
I found out that ACF needs a singular label for displaying the label.