(From the RDB Files)
The context of John 10:33-36 (and of Psalm 82:6 which is quoted there) and NT Greek grammar show "a god" to be the correct rendering. Young's Concise Critical Bible Commentary, p. 62, by the respected trinitarian, Dr. Robert Young, confirms this:
"`makest thyself a god,' not `God' as in C.V. [King James Version or `Common Version'], otherwise the definite article would not have been omitted, as it is here, and in the next two verses, -- `gods .. gods,' where the title is applied to magistrates, and others ...."
It is also admitted that this is the meaning of Jn 10:33 by noted trinitarian NT scholar C. H. Dodd:
"Purely on the basis of the Greek text, therefore, it is possible to translate [John 10:33] 'a god,' as NEB does, rather than to translate God, as TEV and several other translations do. One might argue on the basis of both the Greek and the context, that the Jews were accusing Jesus of claiming to be `a god' rather than 'God.' "- p. 344, United Bible Societies, 1980.
"The word [theos] is used of Divinely appointed judges in Israel, as representing God in His authority, John 10:34" - p. 491, An Expository Dictionary of New Testament Words.
So, in the NEB it reads:
" 'We are not going to stone you for any good deed, but for your blasphemy. You, a mere man, claim to be a god.' Jesus answered, 'Is it not written in your own Law, "I said: You are gods"? Those are called gods to whom the word of God was delivered - and Scripture cannot be set aside. Then why do you charge me with blasphemy because I, consecrated and sent into the world by the Father, said, "I am God's SON"?' "
Not only do we see John using theos in its positive alternate meaning here, but we also see Jesus clarifying it. When some of the Jews were ready to stone him because they said he was claiming to be a god (Jesus' reply about men being called gods in the scriptures would have been nonsensical if he were replying to an accusation of being God), Jesus first pointed out that God himself had called judges of Israel gods (Ps. 82:6)!
Also see: http://examiningthetrinity.blogspot.com/2009/10/theon-rdbs-rule.html