I have a ARC (automatic-reference-counting) app that builds a static library (also ARC). The app will launch fine but when the an action is performed that reads or writes to a @
The app's Base SDK was set to iOS 6 and iOS Deployment Target was set to iOS 5.0 however for the static library both the Base SDK & iOS Deployment Target were set to iOS 6.
Making sure the Base SDK & iOS Deployment Target matched in the app and library solved this problem.