The KJV was an English translation, taken from the Latin Vulgate. It was done during the Protestant Reformation, at the start of the 17th century. At that time, very few textual resources were available to scholars outside of what they already had. The Dead Sea Scrolls were not found until some ~450 years later.
Modern translations (NASB, NIV, ESV, NJB, etc) have gone back and revised their respective translations for accuracy, given the greater amount of material that is now available for cross-referencing. If you compare the KJV to the modern ones you'll find where the KJV had numerous errors throughout it.
I know that the scholars and authors *claim* that they were divinely inspired and that the KJV is the word of God, and can't be refuted. If I claim the same and write something, does that make it irrefutable? :no:
Like I said, keep an open mind and look at the bigger picture.