The libx11-6 postrm script still dies (with my change applied) because /usr/X11R6/lib is the _only_ line in ld.so.conf, and the output file is empty after the fgrep -v. set -e makes the postrm script die.
Suggested change: fgrep -qsvx "$dir" "$ldsoconf" > "$ldsoconf.dpkg-tmp" || echo "empty ld.so.conf!" or some such. Michael