OK, we all know about the change in Empire with the Emperor and the new dialogue. Now, earlier in the movie, when the imperials receive the message from the probe droid about Hoth, Vader says, "...and I'm sure Skywalker is with them." Jump ahead to the new scene.
Emperor, "We have a new enemy...I have no doubt this is the offspring of Anakin Skywalker."
Vader, "How is that possable?"
Emperor, " Search your feelings Lord Vader."
Vader, "He is just a boy. Obi-wan can no longer help him."

So, at first, Vader is looking for Luke. Then, when the emperor tells Vader of the 'new enemy', Vader seems to be clueless. Then, in the next sentence, he is obviously talking about Luke. (I hope you can follow me on this) To me, that whole new scene makes no sense! Does anyone else have another take on this? Or is this just another example of how Lucas screwed up, again?!