[syslinux] syslinux PXE boot version upgrade, network no longer working

[David McDowell]

Hardware with issue is a Lenovo T410 (circa 2007?):

SysLinux PXE boot (pxelinux.0) version 2009 - PXE boot works, select
Ghost from PXE menu, PC-DOS loads, Ghost.exe runs and networking is
working for Ghostcast/peer to peer.

SysLinux PXE boot (pxelinux.0) version 2014 - PXE boot works, select
Ghost from PXE menu, PC-DOS loads, Ghost.exe runs and networking is
NOT working for Ghostcast/peer to peer.

The PC-DOS has a universal network driver (UNDI) 11.1 (boot disk made
from Ghost 11.5 Book Disk Wizard).

My "default" file configuration and .ima floppy disk image are
identical in both environments:

DEFAULT menu.c32
PROMPT 0
TIMEOUT 300
MENU TITLE PXE Boot Menu
LABEL Ghost
 MENU LABEL ^Ghost
 MENU IMMEDIATE
 KERNEL memdisk
 APPEND keeppxe floppy rw initrd=bootimages/ghost.ima

My TFTP is identical in both environments:
TFTPD64 v4.60 Build Jan 28 2017 18:55:26 (Service Edition)

Only difference is the version of SysLinux (pxeconfig.0 and its
corresponding files from 2009 version: menu.c32, memdisk and in the
2014 version add ldlinux.c32).  I have tried with and without
"keeppxe" in the APPEND line.

Interesting side note: Lenovo T420 works in both environments,
networking loads (as do many other models)

Ideas?
thanks,
David