Quando você estiver no live usb, tente os seguintes comentários
sudo -i
apt-get update
apt-get install lvm2
{IF FILE SYSTEM IS ENCRYPTED => DECRYPT}
vgscan --mknodes *##not down the volume name##*
mount /dev/<volume-name>/root /mnt *## For me 'ubuntu-vg' ##*
mount /dev/sda1 /mnt/boot *## fdisk -l for right sd--##*
mount --bind /dev /mnt/dev
mount --bind /dev/pts /mnt/dev/pts
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
cp /etc/resolv.conf /mnt/etc/resolv.conf
chroot /mnt
apt-get update
sudo apt-get install linux-generic
update-grub
apt-get clean
umount /mnt
reboot
[DECRYPT] Se o sistema de arquivos estiver criptografado, descriptografar
apt-get install cryptsetup
modprobe dm-crypt
cryptsetup luksOpen /dev/sda1 crypt1 *## fdisk -l to get right sd--##*
*##Write the passphrase##*
Créditos vão para kyodake por sua resposta a Como reinstalar os kernels