I have an iOS app that worked well on all devices in iOS 6.
I recently upgraded my xcode to version 5.0 and tried to build the same app for iOS 7 on an iPhone 5.
I encountered the same problem and checked if any of the deployment target settings are set below IOS 6.0.
All the above mentioned settings were in order showing IOS 7.0 for all of them. So I looked deeper under the settings tab where I found that I have a sub-entry under release that says "Any Architecture" set to 5.5.1. I changed this to IOS 7.0 and that did the job for me.
Just writing it down here in case I need to look for it again in the future.