XIB File opens like an XML in XCode but opens correctly with Interface Builder

Question

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

Answer 1

For me in Localization section nothing has added.

I had added a new localization English.

Now XIB is shown properly.