[SSP/SMP Mod] Invisible entity in SMP - Need Help!!

Hi,
I've made a client mod witch adds Shurikens in game. It's an item witch launches an EntityShuriken just like if it was a snowball.
It works fine in single player, we can see the shuriken and it does damage.
But once I ported it in multiplayer, it still gets launched, used, and does damage, but it is totally invisible. The entity does not appears at all.
It's registered in client in net.minecraft.src.EntityTypes, and in server in net.minecraft.server.EntityTypes, org.bukkit.entity.EntityType, with a new "org.bukkit.entity.Shuriken" class just like the snowball one, and in org.bukkit.craftbukkit.entity.CraftEntity with a new CraftShuriken class org.bukkit.craftbukkit.entity.CraftShuriken, again like the snowball one.
What did I forget ?
Why does the shuriken does not appears in the game when I play in multiplayer ?
Thanks in advance !

 

You cant add custom graphics

 

What do you mean ? It's just like if I added a new snowball in single and multiplayer.
It is possible, even if I need to mod bukkit a bit to do so.

 

mayby your not sending it whit the packets?