One problem with using a modem cable is that you don't have all the wires in
it that a serial cable can use. Besides the difference that pins 2 and 3 are
reversed between a null modem and an RS232 cable is that the RS232 cable uses
about 4 other wires (I don't remember right now) for signals like DTSR, and
CTSR and stuff like that. I would strongly recommend using a real RS232
cable. If you really need help I can buzz out my cable and give you the
pinouts.