I've had something wierd happen to me a couple of times.  During the 
night, when the daily script is running and the uptime is especially 
high, I would be typing on the keyboard... and then the keyboard would 
lose it's mapping.  All the keys no longer correspond to the keycaps.. 
Like I would press a and get some other character.  The machine itself is 
fine, I can telnet in from elsewhere but the console keyboard no longer 
has its mapping.  I tried killing my processes from outside but at the 
"login:" prompt the console user is not able to type correctly either.  
What could be the cause of this?

--
 o/ \o/  o  <o   o  o   o    She walks in  beauty, like the night
<|   |  /|\  |> <|><|> <|\       Of cloudless climes and starry skies;
/|  / \  /| / \ //  \\ / \   And all that's best of dark and bright
""""""""""""""""""""""""""""     Meet in her aspect and her eyes.  (Byron)