“The failing step is: Install the GRUB boot loader on a hard disk”
Mysteriously, I am not able to successfully reinstall on a machine that previously had a successful installation (15" PowerBook G4 - A1138). The installation proceeds fine until "Unable to configure GRUB. Executing ‘update-grub’ failed. This is a fatal error". Continuing the installation leads to "No boot loader installed; you will need to boot manually with the /boot/vimlinux kernel on partition /dev/sda3 and root=/dev/sda3 quiet passed a kernel argument". I have burnt fresh iso images on a brand new (HP) CD and a new (TDK) DVD, both of which yield the same issue.
"auto" and "expert" install options failed.
"default" install option was successful.
I fixed the problem. The automated install works again. Please read the installation instructions. We now have to manually install debian-system-adjustments.
I only saw your post just now. Next time, if you want a quicker answer, let me know by email that you posted something.