PhoneGap how to make a release build from the command-line
I had the exact same issue. I dont know if my solution applies to your problem. However, here is how I solved it: I suppose you are using the cordova sub project from within your Xcode project. Check if you have the same configuration name for the cordova project.
For example: When your release configuration for your main project is called "ReleaseAdHoc", make sure your cordova subroject also has a configuration with this name. Furthermore, make sure that you select these configurations for the "Archive" process for both, your main project and the subproject.
Hope this helps.