you could just hit F9 for a quick save :/
are you sure you have the absolutly most up to date drivers? if not check the nvidia site
thats all i can think of, sorry i dont have vista
EDIT: actualy i thought of something try running it with JKL (Jedi Knight Launcher) over at
www.jkhub.net its under projects its still a w.i.p. but i noticed that it run JK in a window for the menus so maybe that will help