It was the most literal of dream scenarios. The thing is, it had happened before. From time to time, Valerie Mastromonaco will have a dream--always about a horse--and then something will happen to bring it to life. Nothing dramatic, most of the time. True, once she dreamed that a particular horse in the barn had a problem, and unfortunately turned out to be right. But she doesn't take the phenomenon too seriously, as a rule; nor expect anyone else to do so. "I've no theories," she says. "I just think...