Sorry if this has been posted elsewhere, but i couldn't find it. Twice now, my opponent will stand up and leave the seat. When the next guy sits down, it shows the first opponent's life and avatar, i try to cycle through the turns, it still shows previous opponent on the turn markers.
If you hosted, you can right-click on the seat and vacate it. The new player can then sit in that seat.
However it's normally better to rehost when opponents leave (and yes, it's really annoying when they leave, especially when it's not a computer problem).