I got the above error and after a search, found this link that saved the day:
The steps I took to resolve this were:
1. In Finder, right-click on the xcodeproj file.
2. In the options box, click on Show Package Contents.
3. Right-click on the .pbxproj file and select to open in TextEdit.
4. Do a search on that file for the long string of numbers.
5. Comment out the line and save (add /* before the line and */ after the line).
6. Restart Xcode, reopen the xcodeproj file, and do a Product > Clean. It should start up fine if there were no other problems.