Because this is the very beginning of Closed Beta, there are A LOT of players joining and connecting to the servers.
Additionally, I can't speak from experience, as I haven't been able to play, but I've heard that server lag has gotten worse since the Emerald server was added. On both servers, that is. If you don't have a really solid connection, the server lag may be quite disruptive. Server activity should die down relatively soon (few days?)