I'll take a stab.
In some machines a USB keyboard is not enabled at boot. A 'skip' loading drivers is enabled.
Quote:
"If Enabled, USB devices will not be available until after OS boot, but BIOS will boot faster. If Disabled, USB devices will be available before OS boot, but BIOS will boot slower.
Faster is a relative term in the range of fractions of a second, but it is faster.
A simple test would be to see if you can get into your BIOS from the USB keyboard. If you can't you will need PS/2 keyboard to enable that function. Where it is specifically in your BIOS? I don't know. You'll have to take a look.
If you can get into you BIOS at boot....well, then it's something else.
I have also heard of selecting another USB port for your keyboard may resolve the issue when all else isn't cutting it.