But of course none worked for me :-D.
So I decided to post a solution that worked ;-).
- Boot with any live CD (I've done it with Knoppix 3.x and Ubuntu)
- Prepare directory for mounting:
 $ sudo mkdir /mnt/ubuntu
- Mount the root (/) partition of ubuntu e.g.:
 $ sudo mount /dev/hda5 /mnt/ubuntu
- Mount proc and dev filesystems on mounted partition:
 $ mount -o bind /dev /mnt/ubuntu/dev
 $ mount -o bind /proc /mnt/ubuntu/proc
- If /boot is on seperate partition mount it:
 $ sudo mount /dev/hda4 /mnt/ubuntu/boot
-  Chroot the mounted partition:
 $ chroot /mnt/ubuntu
- Populate /etc/mtab:
 $ sudo cp /proc/mounts /etc/mtab
- $ sudo grub-install /dev/hda
- Exit the shell
- Reboot
 
 
