MrInsaneA said:
I think it's her "Christian Bale Batman Voice."
Love that as a description! Yeah I understand the (contrived) reason for the voice, but it's just annoying and really obvious it isn't her.
If it had been Portman's regular voice but disguising herself with a different, more formal, accent, that would have sold the concept a lot better. The voice we got is just awful though. :-(