Comment 39 for bug 1289977

Same thing occurred when I tried to upgrade ubuntu gnome from 13.10 to 14.04. I've got a dual boot system for year now and it was never considered incorrectly configured in the past, installing and upgrading Ubuntu always worked. I think this bug can't be considered invalid because we have supposedly done something wrong manually. This is not the case if you ask me.

Running boot-repair on a live usb fixed the issue for me, following the provided steps: https://help.ubuntu.com/community/Boot-Repair