The following is an excerpt from Dr. Thomas Holland's Crowned With Glory, ©2000, used with permission.
2 Corinthians 2:17 - "which corrupt the word of God"
"For we are not as many, which corrupt the word of God: but as of sincerity, but as of God, in the sight of God speak we in Christ."
The majority of modern versions render this as "peddle" or "sell the word of God for profit" instead of "corrupt the word of God." The Greek word kapeleuontes does carry the meaning of a peddler or retailer. However, it connotes one who sells with deceit, a corrupter. Dr. Walter Bauer states that the word came to mean "to adulterate."  Dr. Joseph Thayer agrees, noting, "But as peddlers were in the habit of adulterating their commodities for the sake of gain . . . (the word) was also used as synonymous with to corrupt, to adulterate."  Likewise, Dr. Gerhard Kittle states that kapeleuontes, "also means 2. to falsify the word (as the kapelos purchases pure wine and then adulterates it with water) by making additions . . . This refers to the false Gospel of the Judaizers." 
The early church fathers understood the verse to refer to those who corrupt God's word. Athanasius (373 AD) wrote, "Let them therefore be anathema to you, because they have 'corrupted the word of truth'."  Gregory of Nazianzus (390 AD) alludes to 2 Corinthians 2:17, Isaiah 1:22 and Psalm 54:15, using the word "corrupt":
And who is sufficient for these things? For we are not as the many, able to corrupt the word of truth, and mix the wine, which maketh glad the heart of man, with water, mix, that is, our doctrine with what is common and cheap, and debased, and stale, and tasteless, in order to turn the adulteration to our profit . . . 
Both translations are possible. But in light of its historical and contextual usage, the word corrupt is much more likely. Regardless, it is clearly not a translational error. Dr. James R. White, noted Christian apologist and author, makes an interesting claim concerning this verse. He writes, "Surely if the KJV translators were alive today they would gladly admit that 'peddle' is a better translation than 'corrupt,' and would adopt it themselves."  If this is true, how would one explain the notes of Dr. John Bois, one of the translators of the KJV? In his notes on 2 Corinthians 2:17, Dr. Bois writes, "Ibid. v. 17. kapeleuontes ] [being a retail dealer, playing tricks, corrupting] i.e. notheuonetes [adultering]. kapelos is derived apo tou kallunein ton pelon [from glossing over lees] by corrupting and adultering wine."  Apparently, the translators of the KJV were aware of the meaning of this word.
 Walter Bauer, A Greek-English Lexicon Of The New Testament And Other Early Christian Literature, 403.
 Joseph Thayer, A Greek-English Lexicon Of The New Testament (Grand Rapids: Baker Book, 1977 edition), 324-325.
 Kittle, Vol. III., 605.
 Athanasius, Apologia Contra Arianos (Defence Against The Arians), III:49.
 Gregory Nazianzus, Oratition 2 ("In Defence Of His Flight To Pontus"), 46.
 White, 114.
 John Bois, Translating For King James, trans. by Ward Allen. Vanderbilt University Press, 1969), 51.