Well, on the suggestion that was e-mailed to me to try setting:
I tried it, and so far, it seems to be working. As in, I can let a 'ping -f remotehost' (that's attached to the same 100MHz hub as the notebook) go for a while without the interrupt error happening or the network card going silent, and then, on top of that, scp a kernel tarball over from the remote host, too. I'm rebuilding pcmcia-cs with debugging turned off for this card now, and going to see if it still works.
Well, everything seems to be happier now. Right now I'm running a backup of my notebook over the network to my main machine.