Version:           1.0 (using KDE 4.2.4)
Compiler:          Target: x86_64-redhat-linux
OS:                Linux (x86_64) release 2.6.29.5-191.fc11.x86_64
Installed from:    Fedora RPMs

If I login as a normal user I can't send a fax with kdeprintfax. I use it inside KWord. The program reports an error and my fax modem does nothing at all. 
There is no problem if I login as the root !!

That's the log file of kdeprintfax after the error report :

Converting input files to PostScript

Sending fax to 2106778815 ()

Sending to fax using: /usr/bin/fax NAME="'fanisatt'" DEV='ttyUSB0' PAGE='a4' FROM='2221025146'  send '2106778815' '/tmp/kde-fanisatt/kdeprint_60jB5wAf' 
/tmp/kde-fanisatt/kdeprint_60jB5wAf is postscript...
/usr/bin/efax: Mon Jun 22 10:11:43 2009 efax v 0.9a-001114 Copyright 1999 Ed Casas
efax: 11:43 Error: can't open pre-lock file /var/lock/TMP..05925: Permission denied
efax: 11:43 failed -> /tmp/kde-fanisatt/kdeprint_60jB5wAf.001
efax: 11:43 done, returning 2 (unrecoverable error)
There were errors (see T2106778815.log).