Just recently I encountered a boot failure with the following message one or the other, after a few times computer shutdown due to undervoltage which now plagues my area:

error 16 inconsistent filesystem structure
error 18 selected cylinder exceeds maximum supported by bios

I did use live CD to boot and grub
grub> find /boot/grub/stage1
found (hd0,0)
grub> root (hd0,0)
grub> setup (hd0,0)
grub> quit

same problem persisted
then tried
#fsck -f -y /dev/sda1

still the same

then some search in internet indicates it has to do with BIOS setting after the computer failure.

in BIOS setting I noticed 1 setting was reverted back on its own.
SATA mode : SATA
change it to
SATA mode: ACHI

and voila!

Hope this helps.
Wilson

It'a AHCI, not ACHI .

Anyway, glad you could make it and share with us.