Is there a way to restart it to its default settings? i've tried everything else
sudo dpkg-reconfigure xserver-xorg
does not work
If you are using the default opensource drivers or ati/nvidia drivers then one quick way to reset is simply to move to one-side xorg.conf and then reboot i.e.
You rarely need to
If you have been playing with ATI graphics installs then deactivate the driver from the Additional Drivers window and then reactivate to reinstall.
Additionally run the aticonfig routine to generate a new xorg.conf
If you have been playing with NVIDIA graphics installs then deactivate the driver from the Additional Drivers window and then reactivate to reinstall.
You can also remove all references to nvidia kernels install via
Then reinstall the driver from Additional Drivers window.
Additionally run the Nvidia routine to generate a new xorg.conf
Check your cables.
I know this is kind of a off-topic answer, but I spent hours blaming linux for the problem, upgrading and downgrading kernels, nvidia drivers, resetting X.
Turns out the years of linux being terrible with multi-monitor support has coloured my expectations, and once in awhile, a cable just stops working that reliably.