From one day to another the navigation bar disappeared from my storyboard items in XCode 4.6.2. I can't restore them (cleaning, rebuilding, closing, reopening etc)

When running my app on my device or in simulator, everything works ok, the navigation bar is there. But I need them on my storyboard during design time, I have buttons, labels there those must be changed now. (pls. don't advise to do it from code, I want to do it on the storyboard graphically, I think that's why it is there)

How can I get my navigation bars back? I hope the solution won't be to delete/do them again as I read in some places, because I have dozens of navigation controllers.

Thanks in advance!