Here you go, from the
FAQ:
Most text is failing to display on Flash sites!
The plugin has bugs where it makes bad assumptions about the font configuration.
For this reason, it fails to find fonts on newer versions of X.org. You can
workaround this problem in the short-term by using these commands as root.
mkdir -p /usr/X11R6/lib/X11/fs/
ln -s /etc/X11/fs/config /usr/X11R6/lib/X11/fs/config