Comment 8 for bug 551790

I suspect this bug (or one very like it) is what just bit me on the upgrade from Kubuntu 10.10 64-bit to 11.04. It may not be exactly the same though, since in my case the upgrade didn't get confused by multiple valid installs - it just plain picked the wrong drive.

Post-install, the reboot brought up a grub prompt with an "ls /" that listed the contents of an old hard drive I had in the machine with assorted remnants of a previous install's "/usr" directory. For some reason, the upgrade process had decided to nominate /dev/sdc1 as the root of the machine, even though that directory contained no /boot and no /etc. The *actual* root directory (on /dev/sda1) was ignored.

I'm currently still tinkering to get back to a bootable system - I suspect missed some references to the incorrect root partition in my first attempt.