We're in the process of moving to read-only mode as I type this and beginning the move to a new server. Downtime should only be a few hours, and we'll keep everyone up to date here with a series of posts.
update: you might see some session errors as we take the database offline for backup. Logging out should make them go away for now.
update 2: I think I fixed all the session errors. Database is backed up and being moved right now.