I have Windows 8 installed in C drive (by default from Lenovo) & Ubuntu separately installed in another partition.
When I start my computer it leads straight to the GRUB menu. There I can see options to load Ubuntu and Windows 8.
When I select Ubuntu it works fine, but when I select Windows 8 option, then it leads straight back to the GRUB menu.
Hence I am unable to boot into Windows 8 via the GRUB menu (the only way I can boot into Windows 8 is by using the one touch recovery button).