Frequency (H) 31.46KHz ~ 90KHz, (V) 60Hz ~ 75Hz
where H is horizontal and V is vertical
edit ur /etc/X11/XF86Config file with those ranges and it should work fine.. not a big issue
In shell/console you can do,
your file may be /etc/X11/XF86Config-4
I am not sure.Once u edit the file, you can fix the problem.