I gave +1 to @MarkSzymczyk as it pointed me in the right direction, but since it is a bit old compared to the new xcode 5 , I thought I would give an updated answer.
I ran into this problem when I was getting
This document "XXXXX.storyboard" could not be opened. Use the new version of Xcode. Consider changing the design goal of the document to maintain compatibility.
when I looked at my project in xcode 5 and returned to xcode 4.6 . The way to resolve this issue is slightly different from the old xcode . I had to load the project back into xcode 5 and go to the storyboard in the interface builder. It now has a Document Builder Document section instead of a Document Versioning section. It has the ability to change the version of xcode that you want to open. All you have to do is go back to xcode 4.x
I do not want to be distracted from another answer, because he is right, but I just want to expand this answer.
Popeye
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