It was happening to me for a month or so, couldn't log in at all, including today. I inadvertantly found this thread by searching on the scary message and then *not* logging in while reading the thread. Sadly, none of the suggestions here helped (clearing cookies, using my phone, different browsers, etc.) I couldn't even post here about it to tell you.
For me the solution was to use the Reset Password feature and break my normal login method (via my Google account) and set my login to a username/password style login. So far I've been able to stay connected for at least six screens. However, if it kicks me out later, I don't know when/how I'll be able to log in to tell you about it.
If others are finding this thread, but can't log in at all (like me), they might not be able to post here to tell you it's not working for them.