I just switched from Xcode 3 to 4. When I attempt to upload an app that I have archived to the organizer, I receive this error:
The archive is invalid
I had the same issue for both TestFlight and App Store. The solution for me was to archive the app, and in the organizer select "Don't sign" when you try to validate/submit or share (in the case of TestFlight).
Hope this helps.