And rangers have them in their spellbook as well. I've come accross a few others that rangers can't cast but have. Stoneskin is another. Rangers seem to have their own version of some spells, like barkskin and they fall in a divine catagory which I think is part of the problem on some scrolls. As part of the base mechanics, I'm not sure it can be fixed though...
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.
Rangers can now use some additional scrolls: Bull's Strength, Cat's Grace, Barkskin (trade off for not creating a custom Woodland Sheath Scroll) and Stoneskin.
Existing scrolls can be oxed to fix them to make them useable by Rangers if they currently are not.