Got a strange problem with caps lock, num lock and scroll lock LEDs.
When you power the machine up, all three LEDs respond to their
respective keys on the keyboard. However, as soon as the OS has loaded
(in this case NT4 workstation), the LEDs stop responding to key
presses. The status does toggle between the settings, so switching
does occur between caps and lowercase for example, but this is not
reflected in the status of the LEDs.

We have tried various mouse/keyboard combinations which test ok
elsewhere. Also tried re-installing keyboard and mouse drivers.

This is affecting 6 of our PCs so a disk image rebuild would seem like
a sledgehammer approach to such a niggly little problem.