I've now solved this problem. There were old libraries hanging around which I hadn't spotted.
Once I removed the libraries under X11R6 and reran ldconfig the problem was solved. There should probably be some notes or some instructions in the release notes on how to purge old libraries to prevent this kind of issue. OLD: % ls -lAF /usr/X11R6/lib/libfontconfig.so* lrwxrwxrwx 1 root root 20 Jul 13 2004 /usr/X11R6/lib/libfontconfig.so -> libfontconfig.so.1.0* lrwxrwxrwx 1 root root 20 Jul 13 2004 /usr/X11R6/lib/libfontconfig.so.1 -> libfontconfig.so.1.0* -rwxr-xr-x 1 root root 166473 Jul 13 2004 /usr/X11R6/lib/libfontconfig.so.1.0* NEW: % ls -lAF /usr/lib/i386-linux-gnu/libfontconfig.so* lrwxrwxrwx 1 root root 22 Dec 13 2012 /usr/lib/i386-linux-gnu/libfontconfig.so.1 -> libfontconfig.so.1.5.0 -rw-r--r-- 1 root root 215828 Dec 13 2012 /usr/lib/i386-linux-gnu/libfontconfig.so.1.5.0 -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org