i have a HP-Pavilion g6 series laptop with with windows 10 home. Recently i have installed ubuntu 16.04 lts version. after that my keyboard stop working in grub loading menu .after as well as before the grub loading menu ,everything is fine (wireless i ball Keyboard works perfectly) .So i just stuck here in ubuntu not able to load windows 10.My in inbuilt key board and touch-pad is bad (not working). So external keyboard is the only way to operate the laptop.Another problem is that if i change the grub default parameter than there is no way back to ubuntu.

check your bios settings for the keyboard, If I'm not mistaken, grub obtains keyboard info from the bios settings, may also be a usb setting in bios

try to removed or replaced the CMOS battery and put it back in. sometimes it's works.