Woah, never heard of this one before. At least Swedish Wikipedia's got it correctly, so I guess the proper version is what stayed.
Finnish translators somehow managed to muddle up one of the things in Nineteen Eighty-Four. I'm almost too embarrassed to say it...
I have no idea if it were ever changed, but I'm pretty sure there's ever only been two translations. Perhaps Tolkien/his publisher forced mr Misogynist (how is that not a great supervillain name?) to redo that part, though. I can't remember how it went when I read it as a kid.
At least Wikipedia states that Tolkien hated the original Swedish translation and that the new translation is generally considered to be much better. I found no mention of the slayer of the Witch-King being changed, though, but since the translation is known to have many errors I wouldn't doubt it. I also heard that the translator was a prick.
As for the Orwell one... you know that phrase in
Nineteen Eighty-Four: "Freedom is the freedom to say that two plus two make four. If that is granted, all else follows."
The Finnish translation somehow muddled all the instances of that phrase into "Freedom is the freedom to say that two plus two make two. If that is granted, all else follows."
So, the phrase highlighting the right (or lack of) to state even politically incorrect facts became... a phrase highlighting the right (or lack of) to practice bad arithmetic. This makes one of the disturbing mental torture scenes later in the book seem more like a math lesson...