Well, I had a similar problem, with the Micro-Innovations 110Key.
Well, it turns out that the keyboard just "fried", I dont know what happened!
It just stopped working, in Winblows and Linux!
I couldn't even select anything on the boot-menu.
I just got a new keyboard, they're cheap anyway.
(Yes, I did check to see if it was pluigged in)
Hope that helps, although there could be something else wrong instead. I just don't know what!