keyboard problems.

I seem to have an intermittent problem with my keyboard. The c, q, j, comma, down arrow and a few other keys stop working. And then eventually they start working again. They're broken right now but I keep the on-screen keyboard open so that I can say what I want to say. But it sucks. Do you think it's a bad keyboard or some sort of configuration problem? I reinstalled drivers but it seems to have made no difference.