When I try to connect to a server it says:
The server encountered an unexpected condition
It worked a couple of minutes ago.
I have tried restarting Minecraft and my computer, but it still won't work.
This is being caused by some of the Minecraft Services being down.
Basically this is what is happening, when the server goes to authenticate a user it makes a call to Mojangs API to look up the user and then check that information against the users actual login. Since the Mojang servers do not respond the server you are trying to log into has nothing to compare your login information to. Which is unexpected, and it then kicks you back out. Since your account can't be verified.
As you can see: http://xpaw.ru/mcstatus/
The Session is Internaly Down So this means we can;t join :( Sadly