It says the school is Transmutation when I examine it, yet when I attempt to learn it, it states that it is from my mage's opposite school.

Illusion's opposed school is Enchantment, and I've many transmuations, so I am befuddled. Not sure if this is an NWN bug or an EFU one, just thought I'd make note of it.

This is an NWN bug. I don't remember if it's fixed in 1.69 or not.

On a side note, it is fixed in 1.69, yes.