On the 30/03/2013 I plan on removing the current Nether world, and letting the server regenerate a new one. This will allow users to access the new Ores in the nether, and also fix the current state of the nether which is rather bad.
If you have a REALLY important build in the nether, Please ask a Mod+ To copy it over to the main world for safekeeping.
Nether has been removed, But a backup is kept. Survival Nether is now active, And the normal world nether is refreshed.