examples:
Organizer shows for iOS 3.1.3 'The digest is missing' key
It can crash with next crash data:
UNCAUGHT EXCEPTION (NSInternalInconsistencyException): Extension Xcode.Device.iPhone class 'DVTiPhoneLocator' not found for required key 'locatorclass'
For me it happens after run Xcode 6 beta which install incompatible "MobileDevice.framework" on first launch.
so solution:
sudo rm -rf /System/Library/PrivateFrameworks/MobileDevice.framework