PB lancement ubuntu 8.04 via GRUB sur 2ème DD

Bonjour,

Je viens de faire une installation toute fraiche de ubuntu 8.04 sans difficultés particulières mais j'ai un problème au reboot lors du lancement de grub, il demarre "stage 1.5" puis met "error grub" ??

Pour être clair voici le details de mes partitions :

ubuntu@ubuntu:~$ sudo fdisk -l

Disque /dev/sda: 120.0 Go, 120034123776 octets
255 heads, 63 sectors/track, 14593 cylinders
Units = cylindres of 16065 * 512 = 8225280 bytes
Identifiant disque: 0x9f9c9f9c

Périphérique Amorce    Début         Fin      Blocs    Id  Système
/dev/sda1   *           1        2550    20482843+   7  HPFS/NTFS
/dev/sda2            2551       11771    74067682+   f  W95 Etendu (LBA)
/dev/sda5            2551        5100    20482843+   b  W95 FAT32
/dev/sda6            7932       11771    30844768+  83  Linux

Disque /dev/sdb: 81.9 Go, 81964302336 octets
255 heads, 63 sectors/track, 9964 cylinders
Units = cylindres of 16065 * 512 = 8225280 bytes
Identifiant disque: 0x459f459f

Périphérique Amorce    Début         Fin      Blocs    Id  Système
/dev/sdb1   *           1        3647    29294496   83  Linux
/dev/sdb2            3648        3890     1951897+  82  Linux swap / Solaris
/dev/sdb3            3891        9964    48789405   83  Linux

vous pouvez remarquer que j'ai 2 disques dur IDE. Lors de l'installation , j'ai choisi de mettre le programme d'amorçage dans le deuxième disque dur (qui est esclave dans mon bios) soit /dev/sdb . Et malheureusement au reboot grub ne démarre pas :(

Voilà ce que j'ai dans /boot/grub/menu.lst

# menu.lst - See: grub(8), info grub, update-grub(8)
#            grub-install(8), grub-floppy(8),
#            grub-md5-crypt, /usr/share/doc/grub
#            and /usr/share/doc/grub-doc/.

## default num
# Set the default entry to the entry number NUM. Numbering starts from 0, and
# the entry number 0 is the default if the command is not used.
#
# You can specify 'saved' instead of a number. In this case, the default entry
# is the entry saved with the command 'savedefault'.
# WARNING: If you are using dmraid do not use 'savedefault' or your
# array will desync and will not let you boot your system.
default        0

## timeout sec
# Set a timeout, in SEC seconds, before automatically booting the default entry
# (normally the first entry defined).
timeout        10

## hiddenmenu
# Hides the menu by default (press ESC to see the menu)
#hiddenmenu

# Pretty colours
#color cyan/blue white/blue

## password ['--md5'] passwd
# If used in the first section of a menu file, disable all interactive editing
# control (menu entry editor and command-line)  and entries protected by the
# command 'lock'
# e.g. password topsecret
#      password --md5 $1$gLhU0/$aW78kHK1QfV3P2b2znUoe/
# password topsecret

#
# examples
#
# title        Windows 95/98/NT/2000
# root        (hd0,0)
# makeactive
# chainloader    +1
#
# title        Linux
# root        (hd0,1)
# kernel    /vmlinuz root=/dev/hda2 ro
#

#
# Put static boot stanzas before and/or after AUTOMAGIC KERNEL LIST

### BEGIN AUTOMAGIC KERNELS LIST
## lines between the AUTOMAGIC KERNELS LIST markers will be modified
## by the debian update-grub script except for the default options below

## DO NOT UNCOMMENT THEM, Just edit them to your needs

## ## Start Default Options ##
## default kernel options
## default kernel options for automagic boot options
## If you want special options for specific kernels use kopt_x_y_z
## where x.y.z is kernel version. Minor versions can be omitted.
## e.g. kopt=root=/dev/hda1 ro
##      kopt_2_6_8=root=/dev/hdc1 ro
##      kopt_2_6_8_2_686=root=/dev/hdc2 ro
# kopt=root=UUID=5817efec-c8bc-414a-8047-9545ee6ef0dc ro

## Setup crashdump menu entries
## e.g. crashdump=1
# crashdump=0

## default grub root device
## e.g. groot=(hd0,0)
# groot=(hd1,0)

## should update-grub create alternative automagic boot options
## e.g. alternative=true
##      alternative=false
# alternative=true

## should update-grub lock alternative automagic boot options
## e.g. lockalternative=true
##      lockalternative=false
# lockalternative=false

## additional options to use with the default boot option, but not with the
## alternatives
## e.g. defoptions=vga=791 resume=/dev/hda5
# defoptions=quiet splash

## should update-grub lock old automagic boot options
## e.g. lockold=false
##      lockold=true
# lockold=false

## Xen hypervisor options to use with the default Xen boot option
# xenhopt=

## Xen Linux kernel options to use with the default Xen boot option
# xenkopt=console=tty0

## altoption boot targets option
## multiple altoptions lines are allowed
## e.g. altoptions=(extra menu suffix) extra boot options
##      altoptions=(recovery) single
# altoptions=(recovery mode) single

## controls how many kernels should be put into the menu.lst
## only counts the first occurence of a kernel, not the
## alternative kernel options
## e.g. howmany=all
##      howmany=7
# howmany=all

## should update-grub create memtest86 boot option
## e.g. memtest86=true
##      memtest86=false
# memtest86=true

## should update-grub adjust the value of the default booted system
## can be true or false
# updatedefaultentry=false

## should update-grub add savedefault to the default options
## can be true or false
# savedefault=false

## ## End Default Options ##

title        Ubuntu 8.04, kernel 2.6.24-16-generic
root        (hd1,0)
kernel        /boot/vmlinuz-2.6.24-16-generic root=UUID=5817efec-c8bc-414a-8047-9545ee6ef0dc ro quiet splash
initrd        /boot/initrd.img-2.6.24-16-generic
quiet

title        Ubuntu 8.04, kernel 2.6.24-16-generic (recovery mode)
root        (hd1,0)
kernel        /boot/vmlinuz-2.6.24-16-generic root=UUID=5817efec-c8bc-414a-8047-9545ee6ef0dc ro single
initrd        /boot/initrd.img-2.6.24-16-generic

title        Ubuntu 8.04, memtest86+
root        (hd1,0)
kernel        /boot/memtest86+.bin
quiet

### END DEBIAN AUTOMAGIC KERNELS LIST

# This is a divider, added to separate the menu items below from the Debian
# ones.
title        Other operating systems:
root


# This entry automatically added by the Debian installer for a non-linux OS
# on /dev/sda1
title        Microsoft Windows XP dition familiale
root        (hd0,0)
savedefault
chainloader    +1

Merci d'avance pour m'aider à trouver les bons paramètres pour lancer ubuntu 8.04 sur le deuxième disque dur (sdb)