After migrating from XCode 5.0 to XCode 6.0 the project fails to run with the following error.
An error was encountered while running (Domain = FBSOpenApplicatio
iOS Simulator -> Reset Contents and Settings
Worked for me!
iOS Simulator -> Reset Contents and Settings... -> Reset
referenced from: http://qiita.com/tajihiro/items/f6f50b56162c93d25c90