First, you need to quit X
Then you need to be the user
root
Then you need to edit the file
/etc/X11/XF86Config-4
Look for the section like this:
Code:
Section "Monitor"
Identifier "Eizo FlexScan T560i"
HorizSync 31.5 - 82.0
VertRefresh 50-90
EndSection
and change the VertRefresh line to something that you know will work.
Save the changes
Exit from being root
Restart X.