Wuh? When I logged out to get rid of lag due to loading the villagers in spawntown (at least I think that was the cause) and tried to log back in, I keep getting this strange error. I've tried restarting the client, doesn't help.
Edit: From Dinnerbone on twitter (which might not be the cause) "Decided to go play some pvp on some servers with some friends on mumble, but then I accidentally hit quit and the session servers went.
"
Edit2: Looked on the MC forums and it looks like someone else is having the exact same problem, so looks like someone at Mojang accidentially shut off the servers somehow.
Edit3: Yep, theres more people posting the same stuff, so Dinnerbone or someone accidentially shut the servers off.