While i'm playing Minecraft, The game will not let me type a c anywhere.

Put the summary of the bug you're having here

What I expected to happen was...:
It would add the c like any other letter.

What actually happened was...:
It shows a screen to exit and report to mojang.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. Go on a server or add server and type a c in chat.
3. ...