Comment 64 for bug 653134

@elliot, locking grub-pc and grub-common works to prevent boot problems caused by updating those packages. e.g. on a fresh install of Wubi. If you've already updated grub-pc or upgraded to 10.10, then the /boot/grub directory contains all the grub modules - and that results in the buggy grub.cfg file. Locking grub-* won't be enough in this case, you also have to clean up /boot/grub (restore it to what it is on a fresh wubi install).
sudo mv /boot/grub /boot/grubold
sudo mkdir /boot/grub
sudo cp /boot/grubold/grubenv /boot/grub/grubenv
sudo update-grub

The details are describe in the Wubi megathread on ubuntuforums.org: http://ubuntuforums.org/showthread.php?t=1639198