Success! -- of a sort. It turns out pcmcia-modules-2.4.27-2-686 *does* have orinoco.o (for some reason it looked like it didn't). I replaced kernel-pcmcia-modules-2.4.27-2-686 with pcmcia-modules-2.4.27-2-686 . Since orinoco.o is in kernel-image, not kernel-pcmcia-modules, I ended up with two copies of the file, in different parts of the directory tree. depmod and modprobe wanted to use kernel-image's version, so I moved that to my (user) home directory and copied the pcmcia-modules version (/lib/modules/2.4.27-2-686/pcmcia/orinoco.o) to kernel-image's location (/lib/modules/2.4.27-2-686/kernel/drivers/net/wireless/orinoco.o). A depmod later, and Bob, as they say, is your uncle. ifdown eth0, ifup eth1, and I'm no longer tethered.
Thanks, Pete, for your help. -- Michael A. Marsh http://www.umiacs.umd.edu/~mmarsh http://mamarsh.blogspot.com