Brilliant ABT; Cleveland Quartet; limping 'Hypochondriac'; Pro Arte

A healthy, but confused, 'Hypochondriac' ''The Hypochondriac'' (playing at the New Ehrlich Theatre) suffers no lack of vitality. There are problems, but the production, like the patient, is robust and quick-witted.

Richard McElvain has directed Moliere's farce with appropriate speed. Scott Richards plays the ''ailing'' curmudgeon, Argon, whose insistence on being pampered for a plethora of imaginary illnesses creates havoc in his household. Scrawny and querulous, with a bleating voice, he makes a delightful ''invalid.'' His confrontations with the bossy maid, played with a wry earthiness by Bobbie Steinbach, are a match between equals.

Dan Maher plays the young doctor's son whom Argon has chosen to marry his daughter. He fretfully fiddles with his long wig and smirks sullenly, adding a funny (if bizarre) dimension of effeminacy to the simpleton role.

The major problem lies less with the acting than with the overall conception of the production. In attempting to prove that people's obsession with drugs, doctors, and hygiene knows no age, the director has tossed a concoction of all ages at us. An actress dressed in 17th-century costume sports red tennis shoes. The tinkling harpsichord music is produced by a synthesizer. Director McElvain sprinkles contemporary expletives among courtly manners. And Argon's room is cluttered with torturous-looking medical apparatus from various eras. ''The Hypochondriac,'' for all its high spirits, comes off less as being a timeless dilemma than a collection of painful toys. (Through Feb. 26.)