Building from current git (20070202):

Using catalogs: /etc/sgml/sgml-docbook-4.2.cat
Using stylesheet: /usr/share/sgml/docbook/utils-0.6.14/docbook-utils.dsl#html
Working on: /var/tmp/portage/app-doc/xorg-docs-1.4_pre20070202/work/xorg-docs-1.4_pre20070202/sgml/fonts/fonts.sgml
jade:/var/tmp/portage/app-doc/xorg-docs-1.4_pre20070202/work/xorg-docs-1.4_pre20070202/sgml/fonts/fonts.sgml:1923:3:E: "65533" is not a character number in the document character set
jade:/var/tmp/portage/app-doc/xorg-docs-1.4_pre20070202/work/xorg-docs-1.4_pre20070202/sgml/fonts/fonts.sgml:1923:3:E: "65533" is not a character number in the document character set
make[2]: *** [fonts.txt] Error 8
make[2]: *** Waiting for unfinished jobs....
make[2]: *** [fonts.pdf] Error 8
make[2]: Leaving directory `/var/tmp/portage/app-doc/xorg-docs-1.4_pre20070202/work/xorg-docs-1.4_pre20070202/sgml/fonts'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/var/tmp/portage/app-doc/xorg-docs-1.4_pre20070202/work/xorg-docs-1.4_pre20070202/sgml'
make: *** [all-recursive] Error 1

Offending lines are sth like:

1920 <Para>
1921 Unicode (<ULink
1922 URL="http://www.unicode.org"
1923 >&#65533;</ULink
1924 >) is a coded character
1925 set with the goal of uniquely identifying all characters for all

Obviously, &#65533; is intended to interpolate the URI - is this a holdover from linuxdoc?

Currently I'm using this sed:

$ find sgml -name '*.sgml' | xargs -n1 \
sed -e '/^URL=".*"$/{h;s/^URL="\(.*\)"$/>\1<\/ULink/;x}/^>&#65533;<\/ULink$/g' \
-i

There's only 4 instances of this breakage, so I can post a patch if preferred.