Xelatex can't output math symbols when using fontspec. Even leaving the font unchanged and loading fontspec doesn't help. This bug looks essentially like the one described here: https://bugs.launchpad.net/ubuntu/+source/texlive-bin/+bug/364627 If you compile the test file in the bug report, the sum symbol does not display. Unfortunately, the fix described here: http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg631117.html does not work. This is with fully up-to-date F14: [rgheck@rghquad ~]$ rpm -q texlive-xetex texlive-xetex-2007-56.fc14.x86_64