You're probably aware of this, but some laptops (both my last two at least) do not activate the LAN controller if there's no cable/link present at power-on. Warm reboots don't always do the trick either.

Is the laptop getting an IP address? (in the range 192.168.xxx.xxx, not 169.254.xxx.xxx which is the windows auto assignment rubbish) Can you ping the router itself?

Chris