Every time I get on a server and chat Minecraft crashes! This started happening on 1.6.2 and I've never crashed before

Put the summary of the bug you're having here

I was going to play a server (tried multiple)
Describe what you thought should happen here

And I crashed when I said anything.
Describe what happened here

Steps to Reproduce:
1. Get on server.
2. Type in chat
3. Minecraft closes.