title: xib file save doesn't stay saved in Xcode
body: <p>I made some changes to my MainWindow.xib in Xcode and every time I hit save it appears to indicate success, changing from dimmed to normal in the navigator. Seconds later it goes back to dimmed, as if it has been modified and needs to be saved again. Has anybody seen this before? What do I do to make it stay saved.
  I have tried deleting the derived data and reopening the project. The changes do appear to remain as edited, the project compiles and seems to work properly. Only sign of an issue is that the file looks to need saving no matter what I do.</p>
  
  <p>On further analysis I found that it seems to change to modified state whenever I select it, whether I make a change or not. I can't say if this is normal behavior but it does not seem to result in any problems for my project. If I select a different file in the navigator pane, prior to a build, the xib file is saved and stays saved. If I select the xib again after that build, it instantly goes back to modified.
  This does not happen with any other xib files in my project.
  I have never noticed this behavior prior to now, of course it has been ages since I altered this specific xib.</p>