Xcode 4: Archive validation fails because "app.ipa" is missing!

During the archive validation XCode says that the archive is invalid because it misses the "app.ipa" file. How can I get this working?

I created the archive as follows: I used for code signing the AppSore di开发者_开发百科stribution profile for any iOS SDK (under the Release code signing).

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Same problem with "Xcode 4 & IOS 5 beta 2". A rollback to beta 1 worked for me.