I read in David Waite's book 'Defending the King James Version' that the main underlying text for our A.V is Beza's 2nd edition. Yet, upon reading Burgon's 'Revision Revised' I found that the corrupt text 'D', which Burgon calls the worst corruption, is also Beza's.  This leaves me personally puzzled. Is it the same Beza? and if so, what happened between his two texts that they are so very different? 

Theodore Beza (1519-1605) was a well-known Reformer who worked as an associate of John Calvin in Geneva. He was one of several men of this time period who compiled Greek texts of the New Testament. His 2nd edition of this text is the one Waite says was the basis for the King James New Testament (I am not disputing this--just have not studied it completely out myself).

The Codex Beza, though referring to the same man, is entirely differently. It is an ancient uncial Greek manuscript of the Gospels and Acts and is usually designated as D. It is named for Beza simply because he presented it to Cambridge University in 1581 after obtaining it during the French wars in 1562. It is not the same as Beza's Greek text and it is not the basis of the King James New Testament. And, it is very corrupt.