When you join a server with really large map and your internet connection isn't good(I only get 40 kb/s), and you chat/do command before the map is fully loaded, you client won't show the chat. It will show after the map is fully loaded but the server show instantly.

Step to test:

1. Download a large file using custom download client
2. Join a server(Your own server is recommend) with large map.
3. Chat or do command once you joined the server.
4. You will see the chat is not displayed.

Don't get what I mean? Here is a video I made.

http://www.youtube.com/watch?v=JWa_6i2-ays