I'm both running the server on my machine and playing on it, hosting the world that my son logs into from his computer. We're using R2Modman for the file management and both systems have the exact same mods...but he can't see things like the gate expansion items, the "crafty carts" or the item drawers. All mod items and work perfectly on my machine, but he can't see them and, in fact, can shoot arrows through them like they don't exist.

What can I do?