It won't connect to the 'net

The idea is that Apple systems just kind of 'do it' without all the prompting that windows needs. Not here - the ethernet connection I'm using right now, when plugged into the Powerbook, won't do a thing. It's the biggest pain in the ass ever.

I keep on switching the cables over, expecting some light to turn on, some onscreen prompt to pop up and tell me in a campy airline-pilot sort of way "We have a connection!"
But no; nothing happens and I'm stuck here twiddling my thumbs wondering what the hell is going on. The computer realises there's a connection there, it even tells me that the ethernet port is working, but then helpfully informs me that because of a DHCP issue (or something like that) there 'might not' be a connection. This doesn't help me all that much as I can't find a way to resolve it, and don't feel like there's much I can do - especially since the other computer is working just fine.

Eugh, I don't know where to go.