After a fresh install of Ubuntu 14.04 I can't get into my Windows 7 partition. The grub screen appears black with a purple border but I cannot choose anything.
If I try a sudo update-grub then I get a working grub screen but if I run Ubuntu I get kernel panics.
I have similar symptoms. All this happened after upgrade from 13.10 to 14.04. No explanation - pure voodoo.
Grub loads the selection screen. For me Ubuntu boots perfectly. Choosing Windows leaves the screen either purple or purple with black spots. And stays like that. Numlock works, ctrl-alt-del works.
I exercised several different combinations with boot-repair. Restoring MBR instead of grub lead to straight boot into windows as expected. Any other configuration - installing grub in MBR or on linux partition - returned the situation as described in the beginning.
After a desperate attempt of checking keystrokes, I managed to discover an unexplainable (for me) but stably working procedure - when the blank purple screen is reached after choosing windows at grub menu, I hit 'y' - seems to me that it could stand for 'yes' but then it promptly proceeds into windows. Like Magic.
Of course, immediately after posting the above, I found the culprit...
Removing the following line from grub.cfg:
parttool ${root} hidden-
allows me to boot into Windows without pressing any key, just as before upgrading.
