I found the solution, eventually.
I guess that the original driver came up with "No such device" because the pci id on the card was newer than the driver.
After much hair-pulling, I've figured out that the unresolved symbols has something to do with the fact that the system I'm installing on is an Athlon system. To get it to work, I had to copy kernel-2.4.20-athlon-smp.config to .config, make config, make dep, then recompile the driver.
- steve