grub2 - Grub Error in Ubuntu 12.04 after upgrade from 11.10

Boot into the Ubuntu Live Cd and open terminal.



1. Identify Ubuntu partition:

sudo fdisk -l

2. Mount it ( replace sda1 with the Ubuntu partition number):

sudo mount /dev/sda1 /mnt

3.Reinstall grub:

sudo grub-install --root-directory=/mnt /dev/sda
sudo update-grub

Solution from: grub2 - Ubuntu 11.10 not showing up in GRUB bootloader after update and restart :( - Ask Ubuntu.