I originally posted this as its own thread but this thread pre-dated mine, copying my post:
Hello everyone,
You may have been experiencing various issues with your sessions with posting, logging out and potentially logging in as well. Sigmaleph had brought to my attention this error condition.
The issue was sourced from a security upgrade performed on the server hosting these forums. This upgrade broke the webserver's capability to save session files. I have corrected the permissions to re-establish that access and it appears as if the issue has therein been resolved.
Thank you and Securely,
KX.