I ran into a similar error while trying to run "syslinux -i" in TC 14.0 Pure64:
$ sudo syslinux -i /dev/sdb1
Error converting to codepage 850 Invalid argument
Cannot initialize 'S:'
Bad target s:/ldlinux.sys
syslinux: failed to create ldlinux.sys
The short story is that this fixes the problem (run as root, after installing glibc_gconv.tcz):
cd /usr/lib/gconv
mv gconv-modules gconv-modules.orig
cat gconv-modules.orig gconv-modules.d/gconv-modules-extra.conf > gconv-modules
Then "syslinux -i /dev/sdb1" runs without errors.
So /usr/lib/gconv/gconv-modules.d/gconv-modules-extra.conf, which is added by glibc_gconv.tcz, doesn't seem to be read by glibc in TC 14.
Extra info:The error seems to come from the glibc iconv_open function, via mtools, and
this page says: "If the iconv_open returns an error and sets errno to EINVAL, there is no known way, directly or indirectly, to perform the wanted conversion."