[RStar]

Actually, that's what I was going to suggest. Just rip it out, that's what I've had to do.

Sometimes when you take plumming apart little bits get into the pipes and can get into valves, causing them to not close all of the way, and leak or continously run. I suspect this is what happened. The best way to avoid it is to flush the lines the best you can before putting in the new valves.

Hope the new one works for you!