The following might also work for you:

If your touchpad doesn't work at all,
try the command synclient -l | grep TouchpadOff in a terminal.
If you get synclient -l | grep TouchpadOff = 1
then try the command synclient TouchpadOff=0 in a terminal.
If that turns things on (temporarily),
then you will need to add the line synclient TouchpadOff=0
to /etc/X11/Xsession.d/45knoppix to make things permanent.

HTH