i also experience this prob too, but at least my explorer never crash if i cancel. do you get the copy/move thing only when try add multiple file, but not if u add single file? because i got that both way.
however i wonder if this prob cause by hfs. i have keyboard with play button for music player on it. if im working with explorer let say at that time i selecting a few file and i press that play/pause button, the same copy/move dialog appear. this make me think the problem is explorer itself.. i havent install any driver for the keybod