I have a Wester Digital 1 TB Ethernet connected drive on my network. When I plug it into the network I can get an IP from my Cisco Router and/or my Cisco 3560G switch. But when I try to put it on the same network as my LinuxMCE, it receives an IP, but you can't ping it. Linuxmce DHCP shows it handing out a lease to the proper MAC, but it's the "actual" mac. I noticed, Cisco puts a 01 at the beginning and it works fine.
Any reason my WD1TB does not Linuxmce as it's dhcp server?
Are you trying to ping it from your LMCE core? Can you ping it from any other device on your LMCE Internal network (you won't be able to ping it from your external, non-LMCE network)? Can you see the mapping from IP to MAC if you run arp -an on your core?