I have seen this error when I manually built and signed an iOS application bundle using a Makefile. In that case my Info.plist was missing the CFBundleResourceSpecification key (should probably have the value ResourceRules.plist). I did some more testing now and it also happens if the key CFBundleExecutable is missing.
CFBundleResourceSpecification should be added in some build phase by Xcode but maybe it's a good idea to check the resulting Info.plist in the build directory if it's really there.
Maybe this blog post could help, it's about codesign finding the wrong Info.plist file (one without CFBundleResourceSpecification)
http://infinite-sushi.com/2010/08/the-case-of-the-missing-cfbundleresourcespecification/