Problem using keyboard with GRUB

[Jeffery Small]

I have an ASUS U56E notebook set up for dual boot with Windows 7 and
Xubuntu 12.04, using the GRUB version 1.99 boot loader.  I just took the
system in for hardware repair and the motherboard was replaced.

I have an external USB mouse and keyboard attached to the system which work
fine in both OSes.  Prior to the repair the keyboard was recognized by GRUB
and allowed me to make selections using the arrow and Return keys.  After
the repair, GRUB no longer recognizes the external keyboard, although the
native keyboard on the notebook does work.

Does anyone know if there is some GRUB configuration setting I can make to
get the external keyboard recognized once again?  Thanks for any pointers
you can offer.

Regards,
--
Jeffery Small