Comment 3 for bug 1104237

I'm affected by this bug too, running gnome-font-viewer (as root or not) from the CLI gives the same error message but with ":3660".

Also, the article listed in #2 basically tells us to do this:
1: Copy fonts to /usr/share/fonts (or ~/.fonts for user-only availability, no need for root privilages.)
2: Change ownership of the fonts to root (:root, group should be changed too, wasn't); or if you copied to ~/.fonts, you should probably change permissions to allow reads from anyone. (chmod -R a+r ~/.fonts)
3: Run fc-cache. By my understanding, this updates the cached list of fonts available.

Guess that's manual alright..