Unplayable Multiplayer Lag + io.netty.handler.timeout.readtimeoutexception

When I join a server, the map loads really slow like, so I end up falling into the void before anything happens. Sometimes servers allow me to use fly, so I fly up to the loaded chunks of land. When the map's completely loaded, everyone's frozen in place, or walking at an extremely slow pace. I try to survey the area. It would allow me to walk around for a while, but then I get teleported back to the spawn point. Teleport. Teleport. Eternal damnation. Then it would lead me to an error screen with the above message (io.netty.handler.timeout.readtimeoutexception).

This happens to all servers I join. Although 1.6.4 servers work just fine (although I experience a bit of delay).

I do not believe this is of slow internet connection - I still can stream, download, etc. etc. seamlessly as before. This started happening about a week ago. What's wrong with my game?

(In the case my name somehow conflicts with Minecraft sorcery codes, my username is Mycrouft)