I have upgraded a virtual machine running Kubuntu 12.04 to 12.10. After the upgrade completed, I can no longer boot into the OS. After POST, I see three "error: file not found." lines, and Memtest86+ starts up.
I can only assume that the upgrade deleted all kernel images where the installed bootloader looked for them. Luckily this was in a VM and I saved a snapshot before beginning the upgrade, however I would still need to know how to prevent the distribution upgrade from breaking the system again.
Edit: My /boot/grub/grub.cfg before the upgrade.