I think part of this is that some of the spells currently in the Ranger spell list are not, in fact, Ranger spells in default NWN mechanics. Some time ago, we integrated part of a "pseudo-3.5" ruleset that, among other things, bumped rangers a bit including giving them additional spells beyond the normal NWN default spells. Barkskin, for example, is not a standard Ranger spell, and neither is Bull's Strength.
Beyond that, there does seem to be an issue specifically related to Cat's Grace scrolls and Rangers. I see that there is a community (i.e. non-Bioware) patch which allegedly corrects this, though I do not know if it is compatible with our linux server. That's something orth will have to check into.