Ok so the driver built and installed correctly right? If so then is is something simple wrong in the config file can you post the /etc/X11/XF86Config-4 file so we can see it and any lines in the /var/log/XFree86.0.log that have (WW) or (EE) in front of them and the last 15 or 20 lines of this file where it is failing to start.