I've set up four Asterisk PBX, one 1.8 and three 1.6.2 (Ubuntu Server 8.04 / 10.04.4).
I've also successfully set up a chan-mobile with my cell phone (1.6.2) and Google voice channel (1.8 ).
I set up FXO with X100P FXO PCI card for Digium.
I wrote a full guide in Italian how to "install Asterisk on Ubuntu server from scratch", so I'm not a newbie on Asterisk, but I've never been able to set up Free Fax for Asterisk!
I've always found very poor Instructions and bad support for this add-on.
Linux software: "hodge-podge assortments of files, & poor instructions to make something work. Usually many steps are required to get it working & if anything goes wrong you get nothing!"