My guess would be that you're not using the right kind of network lead to connect the Arduino directly to the Network port on your laptop. You would need a "cross-over" lead: http://en.wikipedia.org/wiki/Ethernet_crossover_cable
My guess would be that you're not using the right kind of network lead to connect the Arduino directly to the Network port on your laptop. You would need a "cross-over" lead: http://en.wikipedia.org/wiki/Ethernet_crossover_cable