Explicitly setting LANG=en_US.UTF-8 helped, and installing more fonts (xfonts-terminus in particular) improved things further (didn't work by itself, $LANG really is critical to Xmb* working, it appears.)
Now that I can actually demonstrate it, I'm happy to push the change out, should show up soon. -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org