Thank ou for your help.  I used a usb keyboard and the same thing happened.  I could not log in in safe mode, but I finally hit F12 and ran a complete diagnosis which took hours. It indicated that nothing was wrong, but the keyboard started working.  The next day the keyboard stopped working again.  I repeated the F12 login ran another complete diagnosis and received the same nothing was wrong diagnosis but the keyhboard started working again.  So far it still works.  I am not sure what happened.  What do you think?