I have a Lenovo T520. From time to time (but very seldom), the whole keyboard is no more working (just hangs). It is a problem with X, maybe related to the NVidia driver. In these rare cases I connect a wireless keyboard to the notebook (put the dongle into an usb port) and can go on on typing.
Restarting X initilalises the inbuild keyboard again and then BOTH keyboards are working. The do not interfere. Same behaviour with a cabled usb-keyboard. Best Hans
