I came across this thread because I received the same error, though I do not have the problem the original poster has (my settings are not lost). The first messages I see when starting XnViewMP are:
Fontconfig error: "/etc/fonts/fonts.conf", line 29781727: syntax error
Fontconfig error: Cannot load config file from /etc/fonts/fonts.conf
Fontconfig warning: no <cachedir> elements found. Check configuration.
Fontconfig warning: adding <cachedir>/var/cache/fontconfig</cachedir>
Fontconfig warning: adding <cachedir prefix="xdg">fontconfig</cachedir>
As said, my settings are okay, but I do not see any text (see screenshot).
Bildschirmfoto von »2017-10-02 23-40-08«.png
I tried renaming my config folder anyway because it was suggested in this thread, it was then recreated and the "first start" dialog popped up, but it had no text either except the title.
Also, my fonts.conf is only a few lines long. I am on Arch Linux, too (Antergos, to be precise), and I have the same problem on two different computers. On the first, the problem occured after upgrading XnViewMP, on the second, XnViewMP was not installed before and the problem was there from the beginning as the current version was the first I ever installed on that PC.
You do not have the required permissions to view the files attached to this post.