When it says "messaging" it's talking about messages sent from the client to the server. What's happening is that while you are frozen your client is getting backed up with all of your key presses. Doubly so for holding a direction. When you regain your connection the client spams the server with that queue of key presses/actions.
Basically you're lagging so hard that one way or another, you're going to lose the connection. The error message is a little confusing.