Well, I got the NatSemi network card working on the WRAP board after a lot of confusing tries!
First of all, I had to uncomment the lines for "crc32" and "natsemi" to load the modules at start up - which I forgot to do.
Once I did that, I got some "unresolved symbol" error messages. A post to the LEAF mailing list revealed that I might have different versions of the kernel and modules - which was the case! I had downloaded the latest version of kernel and modules, but used an older version of the WRAP-specific kernel ... which is where the problem was.
I then updated the WRAP board to use the same versions of the kernel and modules, and it worked!
Not only did the natsemi driver work, but I also got the 7DS multicast network working today! It didn't work last week (CRF told me the systems I was using were behind "different switches") but they sure do work now.