Same here. Looks like an update was pushed and no one tested. It won't close, when I click a new game, I get an automatic "Rematch" dialog that exhibits the same behavior. I click refresh and then I can play the next game, however, the "x" to close the window simply isn't working. Can't use the forward and back buttons to look at moves because that thing is in the way.
It's been happening for over a week. Hopefully they won't try and crowd source us for money to fix.
Recently I have been experiencing a problem in which if I click new game button on the pop-up window a new game starts with a pop-up of draw.... I can't even close the window and game just resigns. I have lost countless games due to this and chess.com has banned me for sportsmanship policy please help!!