iOS scheme goes missing when I branch my project (Xcode 4.2)

In Xcode 4.2 when I create a new branch and open it, the iOS scheme which exists in the Master is lost. Instead I have a scheme for 'Mac 64 bit."

This has happened a few times in a row and I handle it by creating a new scheme, deleting the 'Mac 64 bit' one and then renaming the new scheme to what the original was. I'd rather fix whatever is wrong though. Did I set something up wrong - some preference somewhere?