Im not sure what you mean by:
"On win2k with NAT (local IP:192.168.0.150) I setup the internet nic with the above settings"
Is that Win2k Server? Is the SME server replacing that one, or in front of it or behind it? Is that just to test?
Its possible you have a bad network card, a hardware conflict, or a bad cable. Hope you arent making your own patch cords - thats a large source of failure in my experience. You can buy them factory made for a couple of dollars.
Try the nics in other pci slots, and dont use pci slot #1 if you use an agp video card.
As far as setting up clients, just set them to obtain an ip address automatically, and enable DHCP on the SME server. Makes life simple that way...