Was there ever a proper solution to this?
I'm getting the same "Preparing automatic repair" error when I boot W8 from GRUB. No problem if I change the boot sequence so that the W8 HDD is first.
I've disabled W8 fast start-up.
It's a PITA having to go into the BIOS every time.
bootinfoscript results attached. (Had to be zipped because the text file is larger than 19.5kb)