It's kind of a long shot since my installation of LibreOffice outputs few debug messages, but you could try running it from the terminal and see if any output shows up that could shed light on the problem.
Then look at the journal for errors... You'll need to look at messages for the PID that systemd-load-modules ran as. Messages will not show up for the service. 'systemctl status' shows you the pid, and then you can run 'journalctl -b _PID=$pid'
This issue may be related to Syslinux 6.02, which has been identified and fix in the latest ISO. See https://bbs.archlinux.org/viewtopic.php?id=173665 and https://bbs.archlinux.org/viewtopic.php?id=172588 for further information.