I can't chat.

In 1.6 and above, everytime I try to send a chat message my minecraft crashes. In 1.5.2 I just can't send any messages.

What I expected to happen was...:
Describe what you thought should happen here

What actually happened was...:
In 1.6 and above, everytime I try to send a chat message my minecraft crashes. In 1.5.2 I just can't send any messages.

Steps to Reproduce:
1. Send a chat message.
2. Crash
3. ...