I was reminded tonight that newer versions of syslinux (one of my favorites) has broken out libraries from the previous stand-alone modules. Traditionally, for setting up PXE environments all that was needed was pxelinux.0, memdisk, menu.c32, vesamenu.c32. The friendly folks on #syslinux directed me to http://www.syslinux.org/wiki/index.php/Library_modules
Basically now you’ll need:
pxelinux.0, memdisk, menu.c32, vesamenu.c32, ldlinux.c32, libutil.c32, libcom32.c32
in the root of your tftp server.
All of these can be found under the bios directory when you download versions 5 or 6 of syslinux.