Failed to parse existing X config file ‘/etc/X11/xorg.conf’

If you are trying to save your xorg.conf file after changing settings in the nvidia-settings app you may need to first replace it with

> sudo nvidia-xconfig

This will back it up and then recreate it.  Seems a fresh install of Karmic Koala 9.10 doesn’t create a valid xorg.conf or it can’t parse it.  Whatever the case, that’s the fix.

Then you can

> sudo nvidia-settings

To change and save your settings.