2. NSLog output can cause apps to become unresponsive during testing.
If your app becomes unresponsive during testing, check your device or simulator logs for an unusual or a high volume of NSLog output.
It has been demonstrated that a spike in NSLog output can cause the UIAutomation API to become unresponsive. This has been reproduced using the Instruments.app with applications that are not linked with the calabash.framework. This is an Apple bug.