XCode 3 -> XCode 4 = No Files

I have got a small App, developed with XCode 3, in the App Store. Now I want to update some features! In the meantime I have updated to XCode 4.2. It works fine with new projetcs. But: When ever I will open my XCode 3 Project, nothi开发者_开发百科ng happens. The project navigator says:"No files"!

Can you help me!

[This is the link to my Child's Age project. (zip-file) ][1]

[1]: http://files.me.com/rafta2009/h7qkfz

Original Poster has reported that this was the solution to their problem:

Create new Workspace and add your XCode3 App-Folder to the workspace.