Comment 2 for bug 158442

I had a similar thing happen when updating from kernel 2.6.24-2 to 2.6.24-3 using an otherwise (mostly) Gutsy 7.10 installation. The update got both the root drive AND the UUID wrong in menu.lst and so nothing would boot.

The update set all images to boot off hd0,6 (the last drive in the system, actually an NTFS partition) and all UUIDs for the kernel to 29c871f8-fec2-433a-b3ee-db6a5db91b5b, which doesn't match any of the existing UUIDs:

sda1: n/a
sda2: 61556D693E9261F4
sda3: 6f6a8163-c3d6-4086-986b-80da5401cf4e
sda4: 30597d9d-d167-4d42-a19e-5a02de7942a9
sda5: 452fd5dd-4b6c-410f-80ab-245b396fd157
sda6: 560C55ED0C55C89F
sda7: dd9eeb99-91a1-4c12-9b4f-9f2f6e59369e

It should have chosen sda3 (ie hd0,2).

If it's relevant, there is also a /boot/grub/menu.lst on sda5 (ie hd0,4). Updates run from sda3 used to modify the menu.lst on sda5 for some reason but these days they modify the sda3 menu.lst file.

Some version info:

kernel 2.6.24-2
update-inetd 4.27-0.5
update-manager 1:0.81.1
update-manager-core 1:0.81.1
grub 0.97-29ubuntu4