This happened to me once after I restored windows 8 from a previous image I created. Unfortunately, there was no resolution.
I can almost guarantee that if you plug in a USB keyboard it won't work either. I tried that as well, and to my surprise, no keyboards worked. However, it's worth a shot so try it if you have a USB keyboard lying around.
Other than that, you're likely going to have to reinstall windows 8. You can try to reinstall Bootcamp in Safe Mode, but that didn't work for me either.
Keep in mind bootcamp 4.0 doesn't support windows 8; It's somewhat of a minor miracle that it's working right now. Windows 8 isn't officially released until October 26. Until then, and even for a period after, you're what the Industry calls an Early Adopter. These are the pains that early adopters suffer through so that the next generation of users don't experience the same issues. We report the bugs that ultimately get fixed.
Sorry I couldn't be more helpful, but like I said, I've experience the same issue and ultimately had to reinstall windows 8 and bootcamp.