Problem using Zterm program

[Impmon]

I have a Duo 280c (System 7.5.5) and for some reason I couldn't get Zterm to
work at all today.  It refused to believe there is a serial port on my 280c
and only gave me an option: internal 19.2K modem.  The host PC I tried to
connect with was Windows XP running Hyperterminal.  I had everything working
before via serial port but today, no serial port.  I couldn't use modem to
modem connection because for some reason my PC' 56K external has a hard time
with the 19.2K modem and often would drop within a minute of establishing a
connection.  I've tried disabling redundant protocol and resorted to
connecting as low as 9600 bps without luck.

Why couldn't the Zterm find the serial port?  I have no printer installed (I
see a "null" on desktop though but not connected to anything) and Appletalk
was turned off.  So by all account the serial port should have been
available.  And it had been working before.  I hadn't changed any setting
other than mouse speed in the control panel.

I was trying to transfer a bunch of text files to my laptop for reading
later (beside laptop is easier to use on bed than a 20 lbs PC and 19"
monitor ^.^) and I don't have ethernet option for the Duo.  I ended up
having to lug my recently mothballed Duo Dock and used it to transfer the
files.

PS the cable I was using came with my Quicktake 150 for Windows and it was
perfect for PC to Mac serial connection which has 9 pin DB to 8 pin mini
DIN.  An useful tip if you have such cable and frequently connect Mac to PC
without wanting to mess with fussy network protocol or hard to find ethernet
adapter or simply a quick and temporary solution.  Quicktake for Mac would
have only 8 pin mini DIN at both end and not be useable for PC connection.