Comment 2 for bug 495123

i had this issue yesterday too, the only workaround was to uninstall grub2 and install grub(1) then i was able to restart properly.

the exact steps i took was first

use Synaptic to uninstall grub (complete removal)

then i used terminal code

sudo apt-get install grub

sudo grub-update (not sure if necessary but ran it anyways)

then i used the Boot repair tool

sudo add-apt-repository ppa:yannubuntu/boot-repair

sudo apt-get update && sudo apt-get install boot-repair-ubuntu

then access it thru System > Administration > Boot repair

follow directions and it was successful and i was able to restart with no issues.