For those of you wanting to know how to use ARD through a firewall or NAT bridge:
If you wish to use the Remote Desktop application from behind a NAT router, you will need to set UDP port forwarding for port #3283 to your administration computer. If you wish to access a client computer that is behind a NAT router, you will need to set the router to forward UDP port #3283 to the client computer you wish to access. Note: You will be able to access only that client computer.