Wow, thanks!

I've had Knoppix installed for about six months and those gtk-theme-switchers have never worked.

Note to others: the procedure can be summarised as
Code:
sudo mv /etc/gtk/gtkrc /etc/gtk/gtkrc-knoppix
sudo mv /etc/gtk-2.0/gtkrc /etc/gtk-2.0/gtkrc-knoppix