Ballet is a terribly fragile art. Sometimes you can do all the right things and it still doesn't come out right. And sometimes it's next to impossible to say where or how things went wrong -- you just know it didn't work.

Such was the case last night with "Giselle," one of the most frangible of classics, as American Ballet Theatre gave it the first of five performances at Wolf Trap. Externally, in advance, the performance would seem to have had everything going for it, including a cast headed by Marianna Tcherkassky and Fernando Bujones, some presumably revivifying touches in the staging by ABT associate director John Taras, and all the expertise and experience of one of the world's great classical companies. But in the fact, as an emotional experience, it felt flat, almost mummified.

Yes, there were redeeming features. Those in the very sizable audience (a tribute to the still burgeoning appeal of story ballets) who weren't especially familiar with "Giselle" and may have come mainly to see some first-class dancing -- they got their money's worth and maybe then some.

In essence, though, "Giselle" is a danced drama. In its doomed heroine and haunted woods, it's the epitome of balletic Romanticism. The peasant girl Giselle has had her heart broken by the deceitful nobleman Albrecht; driven mad by the revelation of his duplicity, she dies. But the power of her forgiving love reaches beyond the grave to save Albrecht from the vengeance of the ghostly Wilis.

The problem is that only artistry of a supreme order can break through to the universals and save the tale from silliness when it is viewed, as it must be, in terms of contemporary sensibilities.

This doesn't mean one needs "superstars" to elevate "Giselle" to its highest level. Gelsey Kirkland, for example, was scarcely known to the general public when she danced her first "Giselle," which may well have been her finest. Tcherkassky, moreover, is entirely capable of giving a very moving account of the role, as past performances have shown. But that kind of magic, and the emotional chemistry between Giselle and her Albrecht that's an imperative corollary, just didn't happen last night.

Yet one couldn't precisely locate the fault in either the dancing or the acting. Tcherkassky was aptly naive, and then agonizingly distraught, in the first act, and her dancing in the second was at once fey and stalwart. Bujones, an extraordinary technician, a fine stylist and an accomplished actor, also went through the prescribed motions, though he couldn't prevent himself from playing the grand virtuoso in Act 2 just when he's supposed to be expiring with fatigue. Similarly, Cynthia Harvey as Myrta, Leslie Browne as a particularly stirring Moyna, Carla Stallings as Zulma, Clark Tippet as Hilarion and others in supporting roles gave performances of genuine quality. The ensemble dancing has been tidier on other occasions, but that wasn't the real trouble. At bottom, the missing essential was romance.

The production changes seemed relatively minor, and in any case could not have made up the difference last night. The production is a hybrid to begin with, as every production of "Giselle" since the second half of the 19th century has been, and you can get away with nearly anything as long as stylistic consistency and dramatic credibility are reasonably maintained.

ABT artistic director Mikhail Baryshnikov, with assistance from Elena Tchernichova, revamped the choreography and staging in 1980, aiming to mold the ballet closer to the St. Petersburg tradition. Now John Taras has tinkered a bit. The most obvious change is in the "Peasant Pas de Deux," which Taras has made into a quartet and placed earlier in the action. On the one hand, it makes sense to have four dancers instead of two; Giselle and Albrecht are thrown into relief as the couple that way. On the other hand, the thing is a dramatic intrusion no matter how you slice it or where you put it, and adding solo variations for the extra dancers only delays the narrative that much longer. Given all this, the Taras version makes a comely set piece, and Cheryl Yeager, Bonnie Moore, Gil Boggs and Johann Renvall danced it with splendid verve and aplomb.

Taras has also inserted some new dancing for the male ensemble in Act 1 that livens the wine harvest scene a bit without disturbing the context. Albrecht's companion Wilfred seems to do a bit more dissuading in the opening scene than he used to (trying to keep the hero from getting into hot water) -- was this an earlier Baryshnikov touch? Possibly. The other most conspicuous alterations, also perhaps dating from prior revision, are musical additions and substitutions -- disquieting only in the case of the new, equivocal-sounding ending. Paul Connelly ably led the Filene Center Orchestra, which had its troubles with the score.