I've taken the server down to take a quick world backup and perform an update (client update will be released shortly), this should take between 45 minutes and 1 hour.
Apologies for the short notice, updates will be be posted here.
Update - 15:30: The server is back up, but whitelisted while I test the update.
Update - 15:50: The whitelist has been turned off, but a client update is required to join.