I am thinking that your thinking is probably right
Most likely your MB does NOT support that type of chip. I had that problem when I tried to drop a Palimino 1800+ into an Abit KT7A. The board even with the lastes BIOS would NOT reconize the chip. I eventually had to rip my Tbird 1.4 out of my Abit KG7 and swap the processors. Both boards worked fine then
I suspect that the nForce1 chipset just doesnt know how to work with the Tbreds at all.
Sorry
EDIT: I could swap you chips if you want? I have that Palimino 1800+ that I would swap you for that Tbred.