NSManagedObject Error (iPhone)

Question

I'm new to programming, so I apologize for the newb nature of my questions. I'm getting the following error when attempting to run my application I built using Core Data Recipes as my guide.

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '+entityForName: could not locate an NSManagedObjectModel for entity name 'theWho''

I've got an entry in my xcdatamodel for TheWho and I've used theWho and TheWho in different files and set properties to allow them to function, in fact I've changed some of the entries from theWho to TheWho and the error simply changes accordingly.

Where should I start looking in my code?

Thanks