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

This worked for me. i mistakenly got to the blame view when i had this issue,

but clicking on the "show standard editor" worked instantly