How to configure a five button mouse
I inadvertently found a solution to this problem. I installed PCLOS-Gnome after killing my PCLOS installation trying to install Gnome. The Forward and Back mouse buttons worked, out of the box, in PCLOS-Gnome, and not just in Firefox, but also Nautilus. I didn't have a clue what the difference was, but it worked. Being the curious type, I figured it out. Imwheel is preinstalled in PCLOS-Gnome 2008, and is not preinstalled in PCLOS 2007. If you are using PCLOS 2007 you will need to open Synaptic and install imwheel and add the following 2 lines to /etc/X11/imwheel/startup.conf, including the quotation marks.
IMWHEEL_START=1 IMWHEEL_PARAMS="-k -rc /etc/X11/imwheel/imwheelrc.generic"
That is all it takes. There is no need to edit xorg.conf. One more kudo for PCLOS-Gnome 2008, it just works!
Dave