This just started yesterday -- many times when I tried to log in, it wouldn't allow me to. I found that deleting my temporary internet files worked for a short time, but that stopped working. Then I would delete my browsing data and cookies, now that doesn't work either.
Further, when I am able to play, I only get one game in before it freezes. When I reload, it goes back to the log in screen and doesn't allow me to log in.