Yup I've done this myself only recently and the solution is quite simple...but only if there are backups of the X config. file.
at the terminal prompt type:
and you will see a bunch of files...the file we are interested in is xorg.conf
or more importantly other backup versions of xorg.conf that you can find there...are there any??
if so its just a matter of renaming the backup file to xorg.conf overwriting the bad one you had there...and your done.
I'm only a learner myself but hopefully this will point you in the right direction...If not then someone more 'senior' can chime in.