I've seen a similar situation in which the system font "fixed" was not available, and LabVIEW assumes that the "fixed" font is available, but it could also be a locale problem. Did you happen to choose a foriegn local, or UTF*, etc?
Depending on your shell, try setting the "LANG" environmental variable. Like this:
LANG=C labview
Or, simply typing "locale" in a terminal should tell you your current settings.
If that doesn't work, see if you have a fixed font available by typing "xlsfonts | grep fixed".
Let me know if either of those things work for you.