Horses

When I try to tame a horse on a multiplayer game (Lan or Server) I am kicked.

*What I expected to happen was to tame the horse and ride it.

*What actually happened was I got kicked from the server every time I tried to get on.

Steps to Reproduce:
1. Start a server with Minecraft 6.1 snapshot
2. Right click a horse to attempt to tame it
3. Get kicked