The NAB is approved for personal use in its current form. But due to its use of inclusive language, not all of it is approved for use in the Liturgy. The Old Testament (1970) is used because it does not use inclusive language, the new (1991) Psalms are not used at all because they use inclusive language, instead the old 1970 NAB Psalms are used. The current New Testament (1986) is used with some modifcations for the inclusive language.
Now if this is not confusing enough, the NAB Bible is currently going through another revision and is due to be completed in 2010-2011. The New Testament will remain the same, the Old Testament and the Psalms are going through revision.