On p. 233, The Da Vinci Code claims that the divinity of Jesus was decided by "a close vote" at the Council of Nicaea in A.D. 325.
Wrong. It was nearly a unanimous decision. There were over 300 bishops who gathered for the Council of Nicaea. Only two of them refused to sign the creed. I don't know about where Dan Brown comes from, but here in Georgia, 316-2 is not a close vote!
They agreed on the famous Nicene Creed, which reads, in part: "We believe in one God the Father... and in one Lord Jesus Christ, the Son of God... that is the substance of the Father... true God of true God..."
The Council of Nicaea was not convened to discuss if Jesus was divine; it was called to discuss how He was divine. They gathered to express His divinity in theological language to defend against a new heresy of the time, called Arianism. But it was not a suddenly new idea for the early church to say Jesus is God. It goes all the way back to some first century writings known as Matthew, Mark, Luke and John.
(For details on the Council of Nicaea, see W.H.C. Frend, The Rise of Christianity. Philadelphia: Fortress Press, 1984, 498-499)
P.S. The Associated Press published an excellent report today that includes quotes from a liberal Yale scholar who calls the novel's historical background "wildly misinterpreted." It's not just conservative Christians who think The Da Vinci Code has its "facts" wrong. No reputable historian can defend the novel's distortions of history.