The Master Server has been updated for performance reasons – you should hopefully experience “Unable to contact master server” related errors a lot less as a result. I was doing some very, very bad things in the piece of code that ran every time the game client looked up its stats. (Horribly bad. I won't mention the specifics to any other living being: it was just that embarrassing.)
Ranking updates for all players are also temporarily disabled – this will be re-enabled with the release of the rewritten master server, which will take me some time to finish – but I hope that you guys will also prefer being able to play over getting disconnected every other game. Use the statistics website to look up the top 100, and I’m very sorry for any inconvenience caused by the recent server problems.
If anything weird starts happening as a result of this update, please let me know – it would primarily be related to things saying “unauthorized account” upon joining a game.