Pode estar faltando uma partição / boot separada no início do seu disco. Veja o final do seu arquivo de log:
The boot files of [Ubuntu 12.04.1 LTS] are far from the start of the disk. Your BIOS may not detect them.
You may want to retry after creating a /boot partition (EXT4, >200MB, start of the disk).
This can be performed via tools such as gParted.
Then select this partition via the [Separate /boot partition:] option of [Boot Repair]. (https://help.ubuntu.com/community/BootPartition)
Tutorial: link