I experienced a strange problem that ended up having a simple solution. A user called and reported that their keyboard was not responding. The mouse would move just fine, all Task Manager did not show anything unresponsive, but the computer would not respond to any keyboard commands including ctrl+alt+del. Thinking the keyboard probably went bad I grabbed a new keyboard, plugged it in and rebooted the computer. The keyboard worked for a minute then stopped responding again. My first thought was that maybe it was the port itself and not the keyboard so I moved the keyboard to a new port, but no dice, still not working. By this time I noticed a pattern, the keyboard would work just fine when entering credentials, but as soon as the profile loaded the keyboard became completely unresponsive. I logged on to the computer under my own account and as I suspected the keyboard was still working. I deleted the profile of the user who was logging in when the keyboard stopped responding. Boom! Now all of the sudden the keyboard worked just fine. Something in the profile was bad.