It be the minecraft 1.8 pre-release!!!! You gotta replace the minecraft.jar file in ur .minecraft folder, get to it using %appdata% so go to .minecraft - bin
Client - http://assets.minecraft.net/1_8-pre/minecraft.jar
Server - http://assets.minecraft.net/1_8-pre/minecraft_server.jar
Have fun! By the way! Keep a copy of your old minecraft.jar file just incase!
BACK UP FILES INCASE YOU MAKE A MISTAKE.