Are you using HTML editor as a standalone product or part of Data Bridge?
If the former, this could be because the standalone extension is not yet CS6 compatible.
My advice, if you are relying on Dreamweaver for your income then go back to CS5.5 for at least 6 months. I don't mean this from a WA point of view, but from a general point of view. I've found CS6 to be very flakey on the MAC on my test machine and yet everything is purring on CS5.5.