What about a wall mounted AC?
http://www.dcurbanmom.com/jforum/posts/list/308287.page
Does the room have a ceiling fan? I'd look to install one of those first. Also, I think there are fans that work in casement windows, e.g. "exhaust" fan:
http://www.amazon.com/Bionaire-BW2300-Window-Remote-Control/dp/B000065DKJ
I would definitely re-check the wiring/electrical b/f putting in an AC b/c you don't want to overload your electrical box.