From the knoppix cheatcodes:

"In case of a failing hardware autodetection, try booting with any of
the "no-" options as shown in the table above, like in
knoppix noagp noaudio noapm noapic acpi=off nodma nopcmcia noscsi nousb
to skip some critical parts of the autodetection system."

And perhaps even more to your problem:

If you would like to edit your X-Server configuration manually
(/etc/X11/XF86Config-4 for XFree86 V4.x), use "knoppix 2" to boot
into runlevel 2 (textmode only) and, after changing the X
configuration, start the X environment with "init 5". Note that
you can always leave the graphical environment with "init 2", and
restart it later with "init 5".

Note: to edit the Xfree86 file you will need your monitor specs
and some experiance or willingness to learn a text editor.
It would be really helpful for you if someone had a configuration for
your monitor. Still you might just start with the basics to get a usable screen.

See if either or both of those suggestions work and let us know
how you make out. Good luck!