We noticed earlier today that the server was crashing when a particular player logged in, we've now discovered that this seems to be because of a serious chunk loading issue in or near the players region. We are investigating now but the server could be down for some time, I'll update when we know more.
UPDATE: 16:30 - We've found the problem but I couldn't get close enough to remove the offending items, unfortunately I've had to remove a 150 x 60 area from a distance using worldedit and will now have to manually regenerate the missing chunks manually.The server should be back up in no more than 20-30 minutes.
UPDATE: 17:00 - The server is back up and whitelist is removed!
UPDATE: 17:00 - The server is back up and whitelist is removed!
