Hi,
If you click on the very top item (with the app icon) in the files pane on the left, this will bring up a screen in the editor that has a validate settings button at the bottom center. Click that and it will bring down a sheet with suggestions for fixing the app. Just click "perform changes" and that should update it so it runs on Xcode 4.

Hope your problem is solved,
http://www.techyv.com/questions/comp...leopard-64-bit