Try another keyboard. Are you using a cordless or usb type? It's a good idea to always have a basic cheapy standard model in a drawer for troubleshooting purposes. Even you have to borrow one temporarily you still need a working input device there in order to log in. I see this often where you can't even press the F8 key for the license agreement when installing Windows on a new build with the newer style keyboards. A $5-$10 cheapo takes care of that problem fast.