Need help fast -- CoreData error

Question

Hello, need help desperately ahead of a demo in a few hours... App was working on my test device fine last night. Added some data (as I always do) this morning and now I get this error during a save operation:

        Serious application error.  Exception was caught during Core Data change processing:
    *** -[NSCFDictionary setObject:forKey:]: attempt to insert nil value
(key: _ContentChange_OldIndexPathKey) with userInfo (null)

        *** Terminating app due to uncaught exception 'NSInvalidArgumentException',
    reason: '*** -[NSCFDictionary setObject:forKey:]: attempt to insert nil value
(key: _ContentChange_OldIndexPathKey)'

The funny thing is that if I download my sqlite file to my Mac and feed it into the simulator, everything works just fine. The crash only occurs on the test device.

Any ideas?