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 did have this very same issue using xcode_4.2_and_ios_sdk_5_beta__snow_leopard, my working solution.
Install the previous (non-beta) version of Xcode in a different location and work with that version, and that's it, it worked i was able to upload my app to the AppStore without any inconvenience.
regards,
Jorge.