The leaderboard service is under maintenance. During this time, you won't be able to see the leaderboards online.
Statistics are not affected. You can still see your own statistics in-game.
This maintenance may take over 24 hours.
UPDATE: The maintenance is going well, and is about 75% done at this point.
UPDATE 2: Current month leaderboards are back online. Player search, and previous months, are not yet available.
UPDATE 3: Individual player search is back online.
UPDATE 4: Previous monthly leaderboards will become available again over time, however, this automated process may take a few weeks. There will be no further updates.