invalid target for SOME mobs

Well, I am doing the quel dorei quest

I can attacki the ghosts just fine, but the wraiths give out "invalid target"

area spells dont affect them, and they dont aggro me. its not the sticky alt bug, because I can attack and be attacked by other mobs just fine. (including the ghosts in said quest)

Any light on the subject?

Thanks

Check the bugtracker.