Thanks Dave! I was just skimming, now I have to go back and read the whole thread properly
Seriously though, Gino - happy to look at the files and logs with you. Post (in a code block) your /etc/X11/xorg.conf and /var/log/Xorg.0.log files.
And as Dave says, update your driver to the latest version first using the guide in the wiki, I just did this yesterday to 173.14.12 which is the latest version and the guide is acurate and very easy. Don't use the feature to modify the xorg.conf file automatically.
Also, you should put the Option "useedid" "true" in your xorg.conf file (I put it in both the Device and Screen section), then reboot and allow it to start/fail and write the log out. You can then switch to one of the console screens (CTRL-ALT-F2), log in and review the log file, or SSH in and cut and paste the results into this thread.
The UseEDID option just makes sure that X interrogates your screen for its capabilities during mode validation, and sometimes logs useful info that can help use troubleshoot the problem. We can also crank up the verbosity of the logging later if we need to.