I can not chat ANYWHERE!

I can not chat ANYWHERE! Not on servers or even in single player. This problem began at around 1:30PM PST on December 22nd 2013. When I try to chat on multiplayer, I get a message saying "Cannot send message" and on single player it appears as nothing, net even the background shading. I can however still do /msg to other players. I do not have any mods but I have used MCEdit in single player. My MC account is premium and I paid the full $30 to Mojang between December 20-24th 2012.