If you have two mac laptops, I did this on my recent vacation. take the laptop with the working ethernet, and then have that laptop share internet over Airport. It worked every time.

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That would work, but the reason I got the iBook is because I felt the PBG3 was more burden than I wanted to carry.

Why not try booting the iBook off the iMac's HD with target disk mode like I suggested? It would be good troubleshooting.
Also try your Apple Hardware Test CD.

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I have not yet made the hardware test CD, when I make one and I have more time, I will probably do that. Unfortunately my time for tinkering is rather limited. And next weekend is the birthday of one of my granddaughters, so I don't know if I will be able to try these then or not. But, as I said, I have quite a while to solve this. [] ]'>