Occasionally after a hard reboot, next time you startup you’ll get a black screen after grub.
To fix, boot to a live CD, fire up the terminal and do:
sudo e2fsck -C0 -p -f -v /dev/sda1 (might not be sda1 for you)
If this comes back reporting errors, then do:
sudo e2fsck -c -k -v /dev/sda1
