Thanks heaps for your help people! that last suggestion fixed my problem!

log-in screen went back to normal after typing:

sudo dpkg-reconfigure xserver-xorg
sudo nvidia-xconfig
however, when i logged into ubuntu settings were changed back to 800x600, doing a quick search of the forums i came accross someone with the same problem then ran:

gksu displayconfig-gtk
and found my monitor wasnt selected, it was just using a generic monitor, selected my monitor and guess what!? back to 1600x1200.

once again you've all been a great help! thanks alot!!

adios!