Bob58
Did you try:
knoppix vesa, 1024x768
command at boot from cd? If not, give it a try. If it works you need to find out how well and look in the xf86config files and save the live cd config file. Then boot up the hd install and see what is different. The problem with the hd install is that it was set up with different hardware and does not know that it was changed unless you change it in the system files. I would venture to say that the nice new lcd monitor has different refresh and h&v sync rates and that is what you need to change. refer to the monitor manual for that data and change it in your xf86config files. You will have to do it in the lame 640x480 resolution i'm affraid.

I have a sylvania crt monitor, of all the distros of linux that I have none of them even list sylvania as a monitor company. I would venture to say that your wifes lcd monitor is a make that in the list and when knoppix boots, it identifies the correct settings whereas with yours, it does not. You will have to tell it what to use and you can only do that by knowing the monitor info and trial and error.

Also, other distros like SuSE, which is now available as a downloadable iso. have a great installer and hardware tool called Yast. If you have the time and want to see you could let it do it's magic and then mess with the settings in Yast. It allows you to that with the gui up and changes the settings imediately. Then you can know what the xf86files are supposed to look like and try mimicking them in knoppix.