If the games that cause this problem involve using Macromedia Flash, this is a known problem with text display. Try this fix
Originally Posted by http://stanton-finley.net/fedora_core_5_installation_notes.html#Flash
At the moment there is a bug in Flash that prevents it from displaying normal text in FC5. To resolve this enter the following command as root: "mkdir -p /usr/X11R6/lib/X11/fs/", hit enter and then enter the following command also as root: "ln -s /etc/X11/fs/config /usr/X11R6/lib/X11/fs/config", hit enter and then log out and back in.
OR, try updating to flash9 from here: http://labs.adobe.com/downloads/flashplayer9.html
OR try both?
If the games don't involve flash, then obviously just ignore this!