Comment 35 for bug 703009

I think it may be caused by the fact that grub-install does not know
where is the root directory (the partition where /boot/grub is located on).

maybe something like :
     sudo mount /dev/sda1 /mnt # where sdb1 is your root partition (or
boot partition if you have one)
     sudo grub-install /dev/sda --root-directory=/mnt # sda is the disk
where you want to install grub

Or maybe you can do a chroot :
     sudo mount /dev/sda1 /mnt # root partition (or boot partition)
     sudo mount -o bind /dev /mnt/dev
     sudo mount -o bind /proc /mnt/proc
     sudo mount -o bind /sys /mnt/sys
     sudo chroot /mnt
     grub-install /dev/sda # where you want to install grub

Hope it can help someone if it works.