I made a server with the 13w16a snapshot from the .jar file from mojang.com. I made a house with 2 horses. When I right-clicked the horse with a saddle, I was riding the horse and then the server crashed on the client side, it was still running on the server pc, others could connect. The server was still running but when I reconnected the same error came back, every time. I had to remove my name file inside the world folder.

Luuk