Every dance company, no matter how consistenty reliable and spirited, has its drab nights -- last night was one of them for the Joffrey Ballet, performing at Wolf Trap.

Not that anything was particulary amiss with the dancing; quit the contrary. The company, despite or perhaps because of an extensive turnover since its recent furlough for reasons of economy, is looking fit as the proverbial fiddle. The newcomers, many of them young "graduates" of the Joffrey ii troupe, are by and large a handsome lot, agile, vivacious and stylistically well groomed. And their more seasoned colleagues appear to be in excellent shape.

But there is just so much dancers can do to redeem a weak program -- they can, to an extent, rise above their material, but there's no way they can change flimsy or unfocused choreography into something more fundamentally impressive.

What might have been the highlight of last night's fare -- a new, 40-minute ballet called "postcards" by Robert Joffrey himself -- turned out to be pretty much of a total dud, lacking almost all the choreographic virtues Joffrey has demonstrated in the past in such works as "Pas de Deesses, " "Astarte" and "Rememberences."

There's a quotation in the program note that begins "Postcards hold hidden meanings. . . . ". The ballet hides them far too well. All that's presented is a succession of numbers for 19 dancers in varying groupings, by turns sentimental, frisky or playful in tone, and thoroughly undistinguished in design. The choice of unfamiliar songes and piano pieces by Erik Satie was boner to start with; the music has a few moments of wry charm, but is otherwise unrelievedly dull. The front curtain by Joe Brainard, a collage based on Satie mementos, and the interior photo abstraction by Herbert Migdoll, inscrutable in intent, not only clash with each other but also do no- thing to enhance the ballet. The one memorable sequence in this perturbingly aimless piece is a pensive, wistful solo toward the start for Luis Fuente, who briefly manages to suggest a personal poignancy that has no evident connection with what comes before or after.

Neither of the ballets by Ferald Arpino -- the new "Celebration," a frenzied, neo-Slavic romp to inferior music by Shostakovich, and "L'Air d'Esprit," a meretricious "tribute" to ballerina Olga Spessivtzeva -- was much help to the evening. De Mille's "rodeo" is, of course, a masterpiece, though last night's performance was rather humdrum. Coming at the end, though, it only served to accent the anemia of the rest of the program.