Well, it could be a pdflatex bug: Hartmut Henkel jsut found out that pdftex apparently has a limitation of 255 fonts. This might be problematic for languages which use a lot of font planes, like CJK. See http://lists.ffii.org/pipermail/cjk/2006-November/001785.html and further on the CJK mailing list.
Strange thing is that Werner's example zzzz.tex file works on my computer, but on his computer it produces the exact error that I get when pdflatex'ing reference.zh-tw.tex. Perhaps he uses another pdftex configuration. If the creation of the Chinese and Japanese documents is urgent, is it possible to add dvipdfm(x) support? However, a hack in debian/rules or somewhere else will be needed to let DDP use dvipdfmx for zh-tw, zh-cn and ja instead of pdflatex. Also, \usepackage[hypertex,CJKbookmarks]{hyperref} works with dvips, but not with dvipdfmx. dvipdfmx explicitly needs the dvipdfm driver. This could be all too cumbersome to implement. Or perhaps we could temporarily provide the PDF files ourselves, and exclude these three languages from the Debian build process if necessary? Regards Danai SAE-HAN 韓達耐 -- 題目:《示兒》 作者:陸游(1125-1210) 死去元知萬事空,但悲不見九州同。 王師北定中原日,家祭無忘告乃翁。