Sound like it video card is not properly detected or monitor is set to use a refresh rate higher than it can support.
In order for us to help you generate a proper GUI config file, you will need to identify the video card & monitor. To get the video card info, boot off of knoppix CD and do a: lspci -v
Copy & paste the contents here.
Reboot & next from the HD installed system:
Copy the existsing /etc/X11/XF86Config-4 to a back up location.
Code:
cd /etc/X11/
cp -p XF86Config-4 /usr/src
Then try to run the command xf86config. It is a text based question & answer script designed to generate a new config file. It will ask you about the keyboard, mouse, monitor model & refresh rates, video card model/resolution/color depth.
Either myself or someone else will be able to help you along.

I hope this helps.
James