Everytime the nak error happens to me, I read about 100 threads on here about how we should "unblock our ports" whatever that means, and should search the forums, but if you search for nak you get a bunch of unanswered threads. Just go to the tutorial above. It actually gives step by step screenshots and should work for just about every situation.
PS Moderators, if we do as we ought and search for "nak," there are few answers. We are confused by the dozens of closed threads that all point to a FAQ that tells us to open our ports. It makes doing the search more difficult for those of us with due diligence enough to actually search the forum. Thanks.