Just recently I had a power outage and upon starting my machine it failed to boot.
I believe it is the same error that happens here: JayzTwoCents Linux Review
It basically fails to load anything and dumps you into the emergency console.
I got it working by trying to boot into the backup grub entry, having that fail, and then rebooting and trying the normal grub entry. Somehow fixed it.
A few months later I had a hard freeze on my computer and had to switch the computer off at the power supply, and the same problem happened. Again, after the failed boot I reset the computer and tried to boot into the second previous grub entry, had that fail, and then reset again and tried to boot normally and everything worked.
I don’t know if this is a bug, or what, but anyone who is new to linux and has this happen to them would probably switch back to whatever they came from unless they stumbled onto the same sequence of events I did.
So if you have the same problem I did: Reboot and select the second grub menu entry. Let it fail. Reboot and select the normal first grub entry.
I can’t tell you what the problem was, or why that fixed it, but in my case it has worked twice.