I have a problem which is nearly similar to yours:
My e-smith server was a p200 with an Asus Motherboard and a realtek 8139 NIC. I changed the computer to a K6-2 350 with a Fic VA 503+ using the same network card and this time, the e-smith server tells me that this card is unknown. I've tried to use the realtek module as well as the Ne2kpci module: it didn't worked. I've tried with a D-link DFE538TX NIC and it still says 'unknown card'. I only have a PCI graphic adapter and one nic card. As you did, I tried to move the cards but it didn't changed anything.
May be we should assign the irq directly in the module but I don't know how to do it... Any ideas?
Thanks
Mathieu
;o)