From the sound of things you may be having a problem similar to what we had with an on the motherboard NIC by Nvidia. Namely the available drivers for it may not be compiled for the version of the kernel that Puppy is currently using. For awhile we were able to use a driver compiled for the 1.xx series by another user on this board but when the 2.xx series came out the driver no longer worked. What we finally ended up doing was putting in a generic 10/100 NIC card in a PCI slot and using it instead of the Nvidia NIC. For your laptop the only thing I can suggest might be to try a borrowed PCMCIA network card and see if it is recognized. If so then it is a driver issue and maybe someone here can help you identify and compile a driver that will work for your machine. Hope this helps.
Having done considerable googling around about the matter now, I'm certain that's exactly the problem. Unfortunately I don't have access to a PCMCIA card at the moment in order to absolutely rule out other issues.
That's just a pretty common onboard NIC, so I'm surprised there isn't a functioning driver for it.
Yukon driver: 126.96.36.199
Marvell's site does not offer the above driver version for linux 2.4.20 and higher...
If that's likely to be compiled for the next version of Puppy, I can wait 'till then.
Something to address for the next release, perhaps? Lots of laptops with that onboard NIC.