Oops, forgot to paste the part of the code that's blowing up:

[ start code ]

        if (inw(port_base) == 0x6d50) {
                printf("3c5x9 found at %#3.3x.\n", port_base);
        } else {
                printf("3c5*9 not found at %#3.3x, status %4.4x.\n"
                           "If there is a 3c5*9 card in the machine, explicitly set the"
                           " I/O port address\n  using '-p <ioaddr>\n",
                           port_base, inw(port_base));
                if (opt_f < 2)
                        return 1;
        }

[ all done ]

Jared