I know of no general problem at all. What exactly happens? If you get the spinning Castle,
you need to open a private(Firefox) or incognito (Chrome) window , go to dominion.games, enter your Name and Password, but don't click "Login". Instead, click on "Kick and Resign" (small font below the "Sign Up" button). Then you should be able to login normally (no need for private/incognito tab).