The phone has never been jail broken.
I should clarify that the problem is not exactly the same as the OP, I can access my contact list, but not the phone app.
I've just tried wiping the whole phone and booting as a new phone setup without restoring a backup, and the phone works perfectly. So the problem is occurring with the restore process.. So the question remains, how do I get my content and call / SMS history back?
Thanks for your input.