I have been running Windows 8 on a different partition, alongside Ubuntu 12.04, working fine.
sudo apt-get upgrade the Windows 8 partition can't boot. I can still see Windows 8 (on dev/sda3, which is correct) in the grub menu, but when selected I see a black screen flash and the grub menu reappears within a couple of seconds.
I tried repairing with
boot-repair which has always solved my grub issues, but this time it changes nothing.
FWIW here is a BootSummary http://paste.ubuntu.com/5945338