This font can be set in your ~/.Xdefaults or ~/Xresources file. You may have it set to a font that is not installed. To query the font setting, try this in a terminal window:
xrdb -query | grep labelFont
You should see something like this (This is my setting and is probably installed on most systems. I'm assuming your font may be more obscure than this or it may have a spelling mistake in it.):
You can also set the font using these steps:
1. Add the font resource entry to your ~/.Xdefaults file. If a font was returned by the query, don't use it, but use a font that is defined on your system. The xlsfonts command will tell you what fonts are installed. The entry in the .Xdefaults file should be of a similar format to what is shown above.
2. From a shell window, run this command:
xrdb -merge ~/.Xdefaults
3. Restart Cadence to see if it worked.
The font that is correctly appearing in your forms is also a font you can define. Since this font is working, it could be used for your labelFont as well if the helvetica font shown above doesn't work.
xrdb -query Opus
xrdb -query textFont
Hope this helps.