A few minutes ago {as of this post} I was in the midddle
of playing a live-game under one of my temporary handles,
when a window appeared on my screen from a third player
who challenged me to a live game; shouldn't your server
have automatically cancelled that challenge, given that
I was already playing a game on your new Caissa site?!

As programmers say, that isn't a bug, that's a feature! :)
 
On the new site, you can play up to 8 games at the same time. So when you are playing a game, you can still receive and accept challenges. If you do not want to play more than one game, simply decline the challenge. In the future we will add an option to turn off challenges if you are already playing a game.