An iritating bug active since 1.2

Always in multiplayer servers after some time you begin to stand still without moving. You can still walk everywhere and talk to everyone, but if you hit someone it doesn't work, you can't open chests. And if you build things it will be gone after you log in again in the server.

On the screen of others you just stand still and do nothing. So without others watching it is unnoticeable.

With PVP servers you don't die when someone kills you, and you can't kill others. In creative you can build 1 hour making something, but you actually make nothing.