I have installed Windows 8 64-bit and Ubuntu 14.04 64-bit in dualboot with EFI mode.

Everything worked great. I could run Ubuntu or Windows without any problems. Only one little issue was that Windows locked NTFS partitions when I shut it down. When I clicked on restart button in Windows and started Ubuntu, partitions mounted successfully.

But today ... I opened windows and downloaded all available updates. When I wanted to come back to Ubuntu I noticed that grub did not count down seconds to automatic start. After choosing Ubuntu option manually, the OS did not load. Just black screen with white underscore in the upper left corner. Windows is accessible always without such issues.

Last time I solved it by reinstalling ubuntu but I dont want to do it each time windows downloads some updates.

Have you ever meet such problem, or do you know how to solve it?

EDIT

Ubuntu boots, but it won't start. It ends on loading screen.