The extended downtime has now started and investigations are underway, please check back here for updates.
UPDATE: 11:30 - Testing continues, the server will not be back up for at least another 2 hrs.
UPDATE: 12:15 - Good news! World corruption or any other in world cause has been completely ruled out meaning that it's either a corrupt mod / plugin or a hardware issue, testing continues!
UPDATE: 12:55 - I've reinstalled tekkit and the problem still occurs even with a freshly generated world and no plugins, I've notified our hosting company that the problem is definitely not due to anything I have control over, it's in their hands now! Don't worry our world is safely backed up!
UPDATE: 13:20 - There's nothing more I can do now, we're waiting on a response from the hosting company, in the meantime I've brought the server back up and removed the whitelist so you can all login now! BUT the problem is not resolved so be aware that the disconnects we've been experiencing will still occur :( Hopefully we'll get some good news from the hosting company soon!
