The LCD monitors don't require (or tolerate) the high frequencys that you need with a conventional (CTR) monitor. Look at the vertical and horizontal refresh rates in the Section "Monitor" in the XF86Config-4 and change them to :

You can use the terminal and a text editor (like Nano) to change this values in the XWindows configuration file (XF86Config-4).

CategoryRedundant: orphaned page, merge with Xorg