Yikes! I ran into a similar problem with you when I was messing around with my BIOS after my system was built. I disabled my USB controllers to get Windows 7 to install correctly, and I forgot that I would need my keyboard and mouse (both USB). After some hair pulling, swearing, and ground-pounding, I finally remembered that my old computer has a PS/2 keyboard. I simply plugged it in and was able to use that.
As for your care... both PS/2 AND USB doesn't work? Very peculiar, as most BIOS just has an option to disabled USB and not PS/2..
Best of luck though.