My LCD runs at 120Hz. The way it used to work, if xorg.conf didn't include the exact vert and horiz frequencies then refresh rates above 60Hz would not be available to select in the GUI.
(Even my previous 19" LCD ran at 75Hz at 1280x1024)
Actually i think i saw 75hz in the options on mine but its old so i don't mess with defaults, do wish i had a better monitor now though, im sure contrast and colours have improved quite a bit.