When you registered the VMs in ESX did you select Moved VM or Coiped VM? Go into the edit settings and look at the MAC addresses. My guess is that if you copied everythig (including the vmx files) then the MAC address is the same for all the VMs. You can shut down the machines and change the mac addresses to a static MAC address. You could also delete the nics one each, then add new nics. Remember to reconfigure the IP addresses on the box and delete the ghost nics after doing that.
Check this KB for changing mac address.
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=507
Also, Can you log into the switch and look at the ARP table and see if the VMs are registering there.