OK, I followed the advice and just tried it on a spare user machine.
apt-get install nvidia-kernel-2.6.15-grml
That much worked but was not the whole story. Hardware autodetection of the nVidia card seems to be a problem. My current impression is that GRML does not detect it or set it up properly.
At boot time, grml-x creates /etc/X11/xorg.conf. Now as a test, I ran nvidia-xconfig by hand, which creates its own /etc/X11/xorg.conf. Then I rebooted. That didn't work. When I rebooted, X would not start properly. So I fell back to the old xorg.conf.
Even though nVidia drivers are installed, GRML 0.6-1 hardware autodetection fails to use them. Hence it could be considered a bug or missing feature in the hardware autodetection.
Hardware autodetection is the reason I use GRML, and it has the best I have seen, don't get me wrong. There may well be something I am doing wrong, please forgive me if I seem obtuse or dumb, I just report what I see in terms that I understand.
Thanks, Mark