Setting screen refresh in FC2

[fabiano]

I have read older threads (similar for fc3)but I'm not able to solve the 
problem.
I have the right specs for my monitor and video card in xorg.conf.
UNder windows I can set 100Hz at 1024x768 but under fedora  the 
Preferences->screen_resoluzion_tool doesn't permit to set a frequency 
higher than 85 Hz...!!!
If I change to 640x480 (I have 160 Hz under windows) I have the same 
liit of 85Hz!!
I think it is an application bug.
I have searched in x.org configuration manuals ...it was useless.
Has anyone solved this issue???There is a trick???