Fonts lost in Netscape & Mozilla after apt-get upgrade

[Gordon Paynter <gordon.paynter@ucr.edu>]

I've just done an apt-get update & apt-get upgrade for the first time
in a week or two (usig woody), and I've lost the fonts that appear on
buttons in Netscape, and all the fonts in Mozilla.  They're all
replaced by strange little symbols, which I assume means the
characters is unavailable.  All other applications (that I have
noticed) are unaffected, and the Mozilla/Netscape preferences pages
all render correctly.

I don't even know where to begin fixing this.  Deleting the browser
preference files doesn't seem to help.  If I change the fonts in
Mozilla I get some fonts back - even if this worked fully, I cannot
figure out how to change the font on buttons in Mozilla or Netscape.
The 100 dpi fonts all appear to be present and correct (the package is
okay).  

Any help appreciated.

Gordon