I just upgraded my desktop PC from Kubuntu 12.04 64-bit to 12.10 64-bit via Update Manager. Near the end, when I returned to the machine, I saw the last part of a message saying something about grub-pc bug. After reboot, the screen shows "Error 15: File not found".
By the way, I upgraded Kubuntu 12.04 (32-bit) in my laptop using the same method without any problem whatsoever.
Thanks in advance.