I hate to add a "me too!", but everything was fine for me just 16 hours ago and now I get the INV-300 error on attempting to log in. I enabled the work-around, but as YetiGBR3, it's a dangerous thing to leave set.
It's totally my fault - I just got back into EnB this week, so of course the server has to go down when I have my first big block of time to play. I'm sorry.