[CentOS] How do I debug why Centos is asking for fonts to be installed?

Quite a few times a day, both the latest Pan & Firefox 
available in standard CentOS repositories elicit what 
(now) appears to be a CentOS request to install fonts, 
e.g.:  http://i39.tinypic.com/2i7qm2p.png

This latest message says:
 Pan newsreader wants to install fonts
 - Thai
 - Cherokee

At first I had thought it was Pan and Firefox causing 
these messages, but I was just told it's actually CentOS
which is making these requests.

Hence, I ask:
Q: How do I debug why these requests are being made?

And, more importantly:
Q: How do I prevent these messages from popping up?