Hello again!!! There's something strange here, since my /var/log/XFree86.0.log file has some erros at the end related to mouse. The first (EE) line contains xf86OpenSerial: Cannot open device /dev/input/mice No such device and the others that follows are related to mouse too. But I passed /dev/psaux in xf86config. Maybe it's looking for another configuration file instead of /etc/X11/XF86Config. I remember that after using apt-get install x-window-system it started a configuration tools where I've chose the default /dev/input/mice because I didn't know what to choose and I think it's trying to use it but I don't know from what file.
Thanks again!!! -- Henrique