Good call by Gello, I hadn't thought about that. Maybe try removing all other chat windows (default to one) and see if it only gets called once.
If that is still not fixing the problem, maybe try posting the same question in the official WOW forums. Maybe in the 1.7 changes thread. Hopefully Slouken can shed some light as to why the event is called twice for that event.
I tried posting your question with a link back here, but for some reason the forums are not letting me log in right now
