Spells: Vision not working?

[Gaimcap]

So according to the description and from what I read about it on alla, Vision is supposed to grant you vision on whatever target you cast it on.... but for some reason It doesn't seem to do this for me.

It works on myself, but whenever I cast it on someone else I get "You try to cast a spell on Omet[Me], but they are protected."

Ogre Shaman if it matters, Thanks!