Multicast ghost problems

[trick0502]

I am trying to ghost a group of pc's using norton ghost 11.5. I am running into a problem where I can only get two pc's to ghost at a time when i am using multicast. I know the problem is the port security on the cisco switches (each port on the switch is only allowed 2 connections). The port on the ghost server does not have this restriction, all connections are allowed. If i unicast 10 pc's at once that works fine, so i am sure it is the restriction on the ports.

My question is why? Why do I need to remove the port security to get multicast to work?