Try again to use F8 to get to the boot menu. I know it can be hard to get the timing right, but if you can get to the boot menu you might be able to use safe mode to go back to your last restore point and then install the updates one at a time to see which one causes the problem.
The F8 key is not working the screen stays the same, black with a blinking white line at the top. F commands are either not working or whatever is happening will not let me use them. The only F key I can access is the F11 command. When you start the computer it appears that Windows is trying to load then it goes to a black screen with a blinking white line.