Visual Lag/Boat Disappears Upon Restart/Unable to Rejoin LAN Game

While playing latest snapshot on LAN, game started to lag, badly (while rowing back home, video would "rewind" and I would suddenly be taken backwards several blocks). Restarted both computers and restarted game, opened to LAN (I was playing on the LAN) and upon joining the game, my boat had disappeared. Every time I attempt to craft a new boat, LAN game suddenly shuts down with a Timed Out notice. Have been unable to successfully rejoin game for several hours.