After I stopped trying to complicate what the maintainers worked so hard at simplifying, I tried a complete reinstall (several actually) from scratch.
I used Gparted from within the live-cd to:
1.Delete the partitions I want to use
2.Re-create those partitions - formatting as ext4
I restarted the computer and live-cd then when through all of the preparation and update steps (AFAIK).
Then I did a clean install without monkeying with anything. GRUB still would not start.
I then reinstalled Squeeze on the same partitions (reformatted them as ext4) and in the exact same way as I have been trying to do with Siduction. Squeeze booted right up without any problem.
Without changing anything, I reinstalled Siduction in those same partitions (after the preparation and updates). The Siduction installer reformatted the / partition but apparently not the others (which is what I wanted).
The install was reported as successful. The log at the bottom showed GRUB installed in /dev/sda18 (which is the root partition). Even though /dev/sda4 was mounted as /boot, the installer only offers to install GRUB in the MBR or / partition.
When I rebooted the computer, all I got was 'GRUB' with a blinking cursor at the top left of the screen. Apparently there is some problem with using a separate /boot partition for GRUB.
Since all releases of Debian have worked fine with my partition arrangement since Sarge, I am certain there is way to fix this issue. Unfortunately, I do not have the knowledge to do that.
To the best of my knowledge, Siduction is installed fine - it just needs GRUB to work.