"French Postcards" has a promising comic subject: the experiences of American college students spending a year abroad. The opening sequence begins auspiciously by emphasizing the radiant presence of Marie-France Pisier, cast as the co-director of some private academy of learning. She gets embroiled in an argument with a foul tempered tour bus driver while trying to introduce her new American charges to the sights of Paris.

Unfortunately, the premise is quickly betrayed and the radiance dimmed by a hopelessly trivialminded screenplay. "French Postcards" is unlikely to restore the luster to the tarnished reputations of Willard Huyck and Gloria Katz. The personable young husband-and-wife team came to prominence with "American Graffiti," which they wrote in collaboration with director George Lucas, and then came to grief with "Lucky Lady," one of the foremost flops of the decade.

One would expect the Huycks to return to strength on "French Postcards," where the protagonists are young and the material presumably drawns on their own experiences. After all, "Lucky Lady" had been sunk by a fatal lack of comic authenticity. Despite a ton of research, the script remained painfully contrived.

Similarly, "French Postcards," directed by Hyuck and produced by Katz from their own screenplay, begins to founder soon after introducing the principals, three remarkably innocuous and uninteresting young people, impersonated by Miles Chapin, David Marshall Grant and Blanche Baker. The situations these lackluster kids are dumped into prove inexcusably state and shallow.

The boys are incorrigible twerps, the girls a latent bitch. Judging from the smirky, hypocritical preoccupation with sex, the movie might as well have been sent straight to television. Both Chapin and Grant are romantically overmatched: the former with Valerie Quennessen as the daughter of a Parisian bookseller; the latter with older woman Pisier, allegedly available because husband Jean Rochefort neglects her. That is hard to swallow if you share my impression that Pisier is one of the most desirable actresses now on the screen.

While the bland, passive American boys are allowed to wow French-women, in defiance of the apparent cultural and sexual probabilities, the American girl has a rough time even getting a foothold on the continuity. Identified as an undergraduate culture vulture, Baker's character remains on the periphery, supposedly devouring the sights and mailing earnest postcards to her boyfriend back home (thus justifying the title), until late in the story, when she's threatened with A Fate Worse Than Death at the hands of a lecherous Iranian, rather cleverly impersonated by Mandy Patinkin.

The double standard in permissible sexual adventure abroad seems remarkably outmoded for a contemporary setting, harking back to the mores operative at the time "Funny Face" was being made. A more fundamental problem is the casting. Since none of the young leads seems a compelling sex object, maybe the subject of sex should have been avoided. That might have cleared the way for more productive exploitation of the premise, romantic exploitation included.

In a minor role Debra Winger suggests some of the sexual charm and vitality that Blanche Baker seems to be repressing. You suspect she might have enlivened this slumbering farce. At any rate, she's the only one in the cast who recalls the sort of infividuality and humor that informed all the young characters in "American Graffiti."

The production hits rock bottom when Chapin, knowing that fellow student Grant is supposed to be consummating things with Pisier, tries to delay Rochefort from going home in time to discover the hanky-panky in progress. The Huycks seem to have no flair for either inventing or depicting such a bedroom farce crisis. If anything, it appears that they should be actively discouraged from trying to act frivolous or get cute.

The only thing that might reactivate the comic sweetness they're capable of is a determined effort to get straight. Watching "French Postcards," one fears that the opportunity for rehabilitation may already be lost.