Comment 4 for bug 1183392

It appears as though either grub was installed to a disk which is no longer attached to the system, or something went wrong when bringing up /boot.

Could you try to see if the following commands give you any results?

mount /boot
ls -l /boot

I'm reducing this bug importance to High; there isn't sufficient data to be able to consider this a Critical bug, especially since there are apparently no duplicates (I looked quickly and didn't see bugs that had the exact same symptoms), and it seems like the messages on upgrade would have been fairly clear to indicate a major issue during the upgrade. Additionally, what may have caused this seems fairly straightforward, so we'll wait until we hear more from you and bring the importance back up if necessary.

Thanks!