A member on the server found an nasty exploit that let people login as other players (that had migrated their Minecraft account to a Mojang account) but unfortunately, knowledge of the exploit spread like wildfire yesterday. The exploit allowed people to login to servers as the server owner or even as Notch, able to give themselves permissions to do all sorts of damage. The events culminated into the shutdown of Mojang's login session servers several hours in to the drama, and that's where we stand now. If you get a 503 error or an internal error when trying to join, it's because of the login session servers being unavailable. Please login using offline mode (check "Offline" mode under "More options" in the launcher), but you will need your server-registered password on hand. This is also a reminder to keep your registered password current. To set your password (once you are in), you have to use [typed]/register your_password[/typed].
For clarification, the exploit has been fixed. We still suggest that you register using the local authentication plugin.
