Since Masters and Johnson laid the groundwork in the early seventies, therapists have engaged in a radical form of therapy for clients with severe sexual problems. PRIVATE PRACTICES follows two men's therapy from beginning to end. One is a 25-year-old college student who has never dated. The second frets over the breakup of his marriage and fears sexual inadequacy. "I practise sexual and social skills and I try to teach them how to love. I figure if I practise enough, I 'III get it right myself.- "Maureen Sullivan, surrogate