Arduino Mega refusing DHCP address?

Hi all
I have a Mega (clone) and a DeekRobot shield

I got them shipped to work (easier than shipping to home) and had a play over my lunch break

Installed the IDE onto a portable usb (So i could take it home and know I was using the same libraries) and got it connected / dhcp address assigned to it

I took it home, plugged it in and got nothing
So i tried changing the jumper cables i was using, and changing the library
(UIPetherner and EtherCard) and both get no dhcp

I tested the network cable using my laptop and works fine

I even did a packet capture on the wire, and could see the DHCP request from the arduino, and a IP assignment returned from the router, but for some reason the arduino seems to just not accept or get the IP assignment

Im going to take it back to work tomorrow to see if it works fine there to try rule out broken hardware while taking home, and try limit it to my home environment

But does anyone have any ideas why it would be rejecting a dhcp assignment?

Thanks in advance

But does anyone have any ideas why it would be rejecting a dhcp assignment?

Does it reject the assignment? Or simply ignore it? Why didn't you post the sketch and the output of the sketch?