Do you mean "5100" rather than "S100"? If so, you may want to contact Acer. Some people have a problem that kills the keyboard, trackpad and USB ports at the same time, which suggests to me the keyboard & trackpad are on a USB bus internally and it's actually the USB that is failing. You can test that by trying an external keyboard.
I'm assuming you've not pressed Fn-F7 accidentally, of course.
Another random thing you could try: remove adapter, remove battery, reconnect adapter, hold down ctrl while turning the computer on, wait for things to stop happening, turn power off again, turn back on and see if the keyboard's working.