Ethernet not working at home, but did at Genius Bar

hello all,

I have a first gen white macbook. The ethernet hasn't been working with my Airport Base Station for some time (same cable works with an Asus netbook). Nor has it worked in hotels that had wired setups.
I had always assumed it was a defective logic board and would be too expensive to repair out of warranty.

The other day I was at the Genius Bar about a battery related issue and when I mentioned the ethernet port, the guy stated that he had connected to my laptop via the ethernet port to run diagnostics, so it must be working. He suggested I try a different cord (done), and set up a new location (done) but both of those have yet to work.

This is what it shows in About this Mac:

ethernet:

Type: Ethernet Controller
Bus: PCI
Slot: AirPort
Vendor ID: 0x168c
Device ID: 0x001c
Subsystem Vendor ID: 0x106b
Subsystem ID: 0x0086
Revision ID: 0x0001
Link Width: x1
BSD name: en1
Kext name: AirPortAtheros.kext
Location: /System/Library/Extensions/IO80211Family.kext/Contents/PlugIns/AirPortAtheros.k ext
Version: 423.19.10

Marvell Yukon Gigabit Adapter 88E8053 Singleport Copper SA:

Name: ethernet
Type: Ethernet Controller
Bus: PCI
Vendor ID: 0x11ab
Device ID: 0x4362
Subsystem Vendor ID: 0x11ab
Subsystem ID: 0x5321
Revision ID: 0x0022
Link Width: x1
BSD name: en0
Kext name: AppleYukon2.kext
Location: /System/Library/Extensions/IONetworkingFamily.kext/Contents/PlugIns/AppleYukon2 .kext
Version: 3.1.14b1

Any suggestions?