What does your home LAN "look" like?
Do you connect to a router? a DSL modem? or another computer?
Do you have Internet Sharing enabled over the Built-in Ethernet?
Did you enter the IP adress yourself, or did you use DHCP?
What else does NP say when you click on "built-in Ethernet"?
Are those adresses correct?
Are there other computers connected to the internet via the same connection? If so, what are their IP adressses?
What happens if you ping an adress with "Network Utility" (under Applications/utilities). Try
www.mtv.com and, if that doesn't work, it's IP adress: 62.58.34.33
Allright, that's a lot of questions, sorry.