My script is tested with Debian lenny 64 bit. It uses dkms and standard 2.6.26 and 2.6.28 works - now updated to 9-1. Of course when the card has problems the script can not fix driver issues. But the driver install is 100% correct. Tested with

rm /etc/X11/xorg.conf*
dpkg-reconfigure -phigh xserver-xorg

And this script:

http://kanotix.com/files/install-fglrx-debian.sh

To check dkms:

dkms status

module-assistant is completely outdated, dkms is what you really want - boot any kernel (with installed headers) and the driver will work.