The Book of Psalms is filled with drama... for he who chooses to create a Bible Study around it.
Numbering of Chapters
The psalms themselves are numbered differently, depending on whether you follow the Hebrew psalter or the Greek psalter (in the Septuagint). Psalm 9 in the Septuagint is Psalms 9-10 according to the Hebrew psalter; Psalm 113 in the Septuagint is Psalms 114-115 in the Hebrew psalter; Psalms 114-115 in the Septuagint are Psalm 116 in the Hebrew psalter; and Psalms 146-147 in the Septuagint are Psalm 147 in the Hebrew psalter.
As a result, psalms are often listed with another number in brackets (e.g. Ps 110 ) denoting the Greek numbering of the psalm. The Greek numbering is followed in the older Latin Vulgate (although not the Nova Vulgata) and the Douay-Rheims translation.
Numbering of Verses
The New American Bible includes the preface to each psalm (if there is one) as the first verse (in italics); some other translations (such as the RSV-2CE) do not. It appears the NAB inherited this practice from the Latin Vulgate and the Douay-Rheims. The real first verse in the NAB is then listed as verse 2. If the preface is particularly brief, the real first verse is sometimes just appended to the preface and the both of them together are listed as verse 1. However, if the preface is particularly long, it might take up two verses, so the real first verse is listed as verse 3!
So the NAB follows the verse-numbering of the Latin Vulgate, but not its chapter-numbering. And the RSV-2CE follows the chapter-numbering of the NAB, but not its verse-numbering.
Example 1: Ps 110:4 (the same in the RSV-2CE and the NAB (because the preface is so short) and the Nova Vulgata) is Ps 109:4 in the Douay-Rheims and the Latin Vulgate. This would be shown as Ps 110:4.
Example 2: Ps 51:10 in the RSV-2CE is Ps 51:12 in the NAB and the Nova Vulgata (because the preface takes up two verses), and Ps 50:12 in the Douay-Rheims. Would this be shown as Ps 51:10?
Finally, a lot of New Testament references to psalms use the Septuagint. For example, Eph 4:26 refers to Ps 4:4-5 (which verse depends on your translation). The line from Ephesians is translated as "be angry, but do not sin" -- which is found in the Septuagint, but not necessarily in the Hebrew psalm.
What's more, the Extraordinary Form of the Mass uses Psalm 42 (that's Psalm 43 for the rest of us...), and the old Latin of this psalm is a translation from the Septuagint, whereas the Nova Vulgata does not follow the Septuagint here. The first half of verse 4 (across the board) of this psalm in the old Latin is: Et introibo ad altare Dei, ad Deum qui laetificat iuventutem meam. The Douay-Rheims translates this as And I will go in to the altar of God: to God who giveth joy to my youth. The Nova Vulgata, however, reads: Et introibo ad altare Dei, ad Deum laetitiae exsultationis meae. The English translation (in the RSV-2CE) is: Then I will go to the altar of God, to God my exceeding joy.
My head hurts
I wonder why.