"Failed to Log in to Chat and Ladder"
This error message is caused by the inclusion of unsupported characters provided upon log in - typically in passwords. This error was first seen in Patch 0.6.1, and a hotfix was released quickly afterwards to stop it from preventing game access.
The error will still result in no access to social features until we finish work on the chat system which will replace our current one. Currently our recommendation is that you use a different password to workaround the problem.
We take security seriously and correcting this problem is currently our highest priority.