Uploading custom code lists to Nikon DTM-520/522

My firm owns two Nikon totalstations - a DTM-520 and a DTM-522.  We
would like to use a custom code list in each one.  I've created a
sample code list, and have tried uploading it to the DTM-520, but each
time I upload it, I receive an error (which I did not write down, and
do not have handy, sorry - I'll try to get it tomorrow).

The error seems to indicate a problem with my code list on a certain
line.  However, no matter what I do, this error persists.  I finally
stopped adjusting my code list, and started playing around with the
communication settings, and with each change to the comms settings,
the upload stops with the same error, but at different lines in the
code list, which indicates to me that the problem is with the comm
settings, not the code list itself.

The 520 uploads and downloads coordinate points without a hitch at
various speeds, and has done so for a couple of years now for us, so I
know that the cable and comm settings are correct.  I'm trying to use
Win98se and Hyperterminal to send the code list (using the Send Text
File) option up to the 520.  Does anyone know of some "magic" settings
that will make this work, or should I be trying some communication
program other than Hyperterminal?

The Nikon manual is very sparse, and nobody at Nikon has seen fit to
reply to my email to them regarding this matter, so I'm open to any
suggestions.  I used to be a computer consultant in Toronto for 11
years before turning to surveying, so I'm very familiar with trying to
resolve problems like this, but I just haven't had any luck so far. 
Any ideas?

Thanks
Chris Bunker