title: XIB File opens like an XML in XCode but opens correctly with Interface Builder
body: <p>When I double-click my file StartWindow.xib in Xcode 4, it does not open into the integrated Interface Builder; it opens like a XML file. I can open all other xib files and they display as expected. I can open it with the old Interface Builder via "Open with".</p>
  
  <p>What can I do to open it with the integrated Interface Builder?</p>