Can a prim, impotent young German-Jewish (""Quaker"") architect find happiness with an earthy Brooklyn-Jewish cabaret singer? That's the less-than-riveting central question in this Upper West Side sit-com-mit-psychopathology--heavy on brand names, show-bizzy chatter, and campy (occasionally funny) one-liners. Michael Bauer, 30, is handsome, talented, and wealthy (a trust fund he doesn't touch). But, as his bisexual chum Lewis says, Michael is ""terribly fucked up and fucked over. . . a Gary Cooper for today, if Gary Cooper were depressed and sexually ambivalent."" Is Michael really gay? Despite his edgings in that direction (letting himself be half-seduced, gay-bar-hopping), he thinks not. Why, then, is he now impotent--even with nice, plumply sexy torch-singer Anna Diamond? Well, it probably has something to do with his mother's early death, his fear-of-abandonment, his failure to rebel against his oppressive, proper father (now seriously ailing) and his married sister (always seriously obnoxious). So, while Michael broods self-deprecatingly, Anna tries to be patient and loving and non-pressuring; when Michael virtually disappears (exploring his homosexual potential), she does opt for a consummated one-night-stand with a Jewish pilot. Finally, however, after more postponements than a Barbara Cartland romance, their true love conquers all--including (without much down-to-earth plausibility) Michael's sexual problems. Throughout, in fact, Gelb takes an unsatisfying middle course in dealing with the impotence question: too clinical to fit the overall breezy comedy, not clinical enough to make Michael's ""quantum leap"" into happiness convincing. (On the evidence here, one expects Big Problems ahead for the Michael/Anna match-up.) And if Michael is too severely troubled for such a chirpy, TV-movie-ish diversion, insecure/brash Anna is an all-too-familiar stereotype--thanks to Gail Parent and others. Still: some N.Y.-provincial readers will be satisfied by the energetic parade of fat jokes, therapist jokes, Jewish-mother jokes, preppy jokes, movie-buff jokes, etc.--while Gelb shows glimmers of more substantial talent in the treatment (a ghastly Christmas dinner especially) of Michael's stultifying Westchester family.