Those errors usually mean websockets are not proxied correctly, make sure your nginx setup is correct. If you are using cloudflare you need to disable acceleration. They don't support websockets on smaller plans.
Ok, so further testing indicates that it only happens on users that were created in 0.6.1(via an import from SMF) and new users work fine. I can fix it by blanking out the user's email and then putting back in the correct email.
(For clarification this is running on a pull from the 0.7.0 dev branch from yesterday)