Patience, Turbine's Community Manager for Lord of the Rings Online, warned us about downtime tomorrow:

The LOTRO game servers will be brought down from 12:00PM - 4:00PM for a hotfix to the game. Details of the hotfix will be released when the servers come back up.

Roheryn will remain available during the downtime, with a special "Open House" event to preview Player Housing in Book 11: Defenders of Eriador. For more information about the event, and how to download the Roheryn client, please see this post on the forums!