Thank-you. The valve is 30 years old, so you are probably right that it could use a replacement.
Why would one tap be running and the others dry? It would have to have bypassed the (dry) kitchen tap, which is the closest to the water line.
Well, my friend worked on the faucet (which is why we turned the water off in the first place) and after I turned the water main on and then off again, it was coming out of the bathroom sink tap and the tub was dry.