With the little understanding I have so far of Linux, according to my SysLog this is where grub-install screws up (/sda8 & /sda9 being IBM's JFS):

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Apr 29 04:55:06 ubuntu grub-installer: info: Installing grub on '/dev/sda9'
Apr 29 04:55:06 ubuntu grub-installer: info: grub-install supports --no-floppy
Apr 29 04:55:06 ubuntu grub-installer: info: Running chroot /target grub-install  --no-floppy  "/dev/sda9"
Apr 29 04:55:08 ubuntu grub-installer: Probing devices to guess BIOS drives. This may take a long time.
Apr 29 04:55:09 ubuntu grub-installer: Searching for GRUB installation directory ... found: /boot/grub
Apr 29 04:55:15 ubuntu grub-installer: Installing GRUB to /dev/sda9 as (hd0,8)...
Apr 29 04:55:16 ubuntu grub-installer: 
Apr 29 04:55:16 ubuntu grub-installer:        [ Minimal BASH-like line editing is supported.   For
Apr 29 04:55:16 ubuntu grub-installer:          the   first   word,  TAB  lists  possible  command
Apr 29 04:55:16 ubuntu grub-installer:          completions.  Anywhere else TAB lists the possible
Apr 29 04:55:16 ubuntu grub-installer:          completions of a device/filename. ]
Apr 29 04:55:16 ubuntu grub-installer: grub> root (hd0,8)
Apr 29 04:55:16 ubuntu grub-installer: grub> setup  --stage2=/boot/grub/stage2 --prefix=/boot/grub (hd0,8)
Apr 29 04:55:16 ubuntu grub-installer:  Checking if "/boot/grub/stage1" exists... yes
Apr 29 04:55:16 ubuntu grub-installer:  Checking if "/boot/grub/stage2" exists... yes
Apr 29 04:55:16 ubuntu grub-installer:  Checking if "/boot/grub/jfs_stage1_5" exists... yes
Apr 29 04:55:16 ubuntu grub-installer:  Running "embed /boot/grub/jfs_stage1_5 (hd0,8)"...  18 sectors are embedded.
Apr 29 04:55:16 ubuntu grub-installer: succeeded
Apr 29 04:55:16 ubuntu grub-installer:  Running "install --stage2=/boot/grub/stage2 /boot/grub/stage1 (hd0,8) (hd0,8)1+18 p (hd0,8)/boot/grub/stage2 /boot/grub/menu.lst"... failed
Apr 29 04:55:16 ubuntu grub-installer: 
Apr 29 04:55:16 ubuntu grub-installer: Error 6: Mismatched or corrupt version of stage1/stage2
Apr 29 04:55:16 ubuntu grub-installer: grub> quit
Apr 29 04:55:16 ubuntu grub-installer: error: Running 'grub-install  --no-floppy  "/dev/sda9"' failed.
Apr 29 04:58:13 ubuntu python: log-output -t ubiquity umount /target/cdrom
Apr 29 04:58:13 ubuntu finish-install: Disabling CD in sources.list
Apr 29 04:58:13 ubuntu python: Exception during installation:
Apr 29 04:58:13 ubuntu python: Traceback (most recent call last):
Apr 29 04:58:13 ubuntu python:   File "/usr/share/ubiquity/install.py", line 2225, in <module>
Apr 29 04:58:13 ubuntu python:     install.run()
Apr 29 04:58:13 ubuntu python:   File "/usr/share/ubiquity/install.py", line 435, in run
Apr 29 04:58:13 ubuntu python:     self.configure_bootloader()
Apr 29 04:58:13 ubuntu python:   File "/usr/share/ubiquity/install.py", line 1659, in configure_bootloader
Apr 29 04:58:13 ubuntu python:     "GrubInstaller failed with code %d" % ret)
Apr 29 04:58:13 ubuntu python: InstallStepError: GrubInstaller failed with code 1
Apr 29 04:58:13 ubuntu python: 
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Why/how is this failure happening and what do I need to do, in order to finally get Jaunty somehow installed?
PS: The GRUB bootloader must be in a PBR and not the MBR, the fs must be JFS and not ext[n] or whatever.