Peculiar effect with keyboard

[Simone Bowskill]

Hello All
I am sending this from my Wife's computer because of the effect 
explained below:

On start up, I reach the normal login screen and can log in normally - 
from the keyboard.
When the full normal window manager display comes up the keyboard goes 
dead - the mouse is OK.
I then restarted and selected "repair broken packages", then "normal 
start" - the same effect was present - no keyboard.
Restarted again but entered terminal mode - the keyboard behaved perfectly.
Exchanged the keyboard with one that is OK (the one I am sending this 
message on) - same result as before.

It would seem that when the X-server/window manager starts, the keyboard 
becomes disabled.

Has anyone any ideas what would cause this and how I can fix it ??

Many thanks in anticipation

David Bowskill