title: Xcode Interface Builder is showing "No selection" for all files
body: <p>No matter what I've got selected in Interface Builder, the Inspector did apparently not register the selection and only showed "No selection". </p>
  
  <p>I tried opening and closing files, restarting Xcode and even rebooting my Mac. No change! What the heck is going on?</p>
  
  <p>Other projects work just fine. It's just this project...</p>