I think all Bibles are to some extent or another flawed in their translations. I also think that each has its merits, in some case or another proving to be more accurate than others. With respect of the NIV, I have found it to be the MOST ACCURATE translation regards Job 1 : 6. There is also a passage in Isaiah which contains a double entente. Only the NIV has successfully preserved both meanings amoung the 7 versions I have. That said I regard the Jerusalem Bible as being the MOST ACCURATE overall, with the New Revised Standard being the runner up amoung the versions I have.
See Genesis 6 1 - 4 : (Sons of God and daughters of men a) Jerusalem Bible
Genesis 6 1 - 4 : When men had begun to be plentiful on the earth, and daughters had been born to them, the sons of God, looking at the daughters of men, saw they were pleasing, so they married as many as they chose. Yahweh said, "My spirit must not forever be disgraced in man, for he is but flesh; his life shall last no more than a hundred and twenty years". The Nephilim were on the earth at that time (and even afterwards) when the sons of God resorted to the daughters of man, and had children by them. These are the heros of days gone by, the famous men.
Note : TheJerusalemBiblecrossreferencesthe foregoingpassagewithJob1,Wisdom 146, 2 Peter 2 2 - 4, Jude 6, Deuteronomy 2 10, and Baruch 3 2 ; which are all passages which refer to the offspring of these unions as "Giants".
See Job 1 6 : Jerusalem Bible
Job 1 6 : One day the Sons of God came to attend on Yahweh and among them was Satan.
Note : The King James, The Darby, The Revised Standard, and The New American Standard Bibles all agree with the Jerusalem with reference to the term "the sons of God". The New Revised Standard, however, substitutes "the heavenly beings" for "the sons of God". Although the former provide a connection to the reference to "the sons of God" as mentioned in Genesis 6 1 - 4, I believe the most accurate translation for both passages may be found in the New International Versions rendition of Job 1 6.
See Job 1 6 : New International Version
Job 1 6 : One day the angels came to present themselves before the Lord, and Satan also came with them.
Note : From the immediately foregoing it may be seen that the "sons of God" who "resorted to the daughters of man, and had children by them", were actually "angels".
See Jude 6 : Jerusalem Bible
Jude 6 : Next let me remind you of the angels who had supreme authority but did not keep it and left their appointed sphere h; he has kept them down in the dark, in spiritual chains, to be judged on the great day.
Note h : They let themselves be seduced by the "daughters of men", Gn 6:1-2; the subject is elaborated on in the Book of Enoch.