The idea of Heather Graham and Bridget Moynahan locked in a Sapphic embrace may have excited more than one of the makers of “Gray Matters,” but it is not a gimmick that keeps on giving. In fact, by the time the kiss arrives, the film has compiled a list of annoyances too great to be derailed by a shallow attempt at titillation. Instead, “Gray Matters” becomes a reminder of why Ms. Graham does not headline movies more often.

The film casts Ms. Graham as a 30-something advertising executive named Gray who lives with her brother Sam (Tom Cavanaugh) and refers to herself as a charming hotel that is “closed for repairs.” After one too many insinuations that the siblings are incestuous, Gray decides to find them both mates. She procures a beautiful marine biologist named Charlie (Ms. Moynahan) for her med student brother. But as quickly as the two meet, inexplicably fall in love, and get engaged, Gray realizes that she has also fallen for Charlie and is in fact gay.

After a protracted kiss scene between Gray and Charlie — which has already made its way to YouTube — Gray spends the rest of the film trying to make sense of her sexuality, to the detriment of the audience.

First-time writer and director Sue Kramer packages this story of postponed sexual realization as a cute romantic comedy, but stuffs the film with enough awkward and contrived set pieces to fill an entire season of UPN programming.

Unlike other mainstream lesbian flicks, like “Chasing Amy” and “Kissing Jessica Stein,” which document their heroines’ flirtations with homosexuality before finding a good man, “Gray Matters” is adamant about its protagonist’s preference for her own sex. But it isn’t similarly dedicated to making her sympathetic. Gray is painfully indecisive, twitchy, and neurotic. And the film’s overbearing script and undercooked jokes only work to expose the glaring deficiencies in its star. Despite her natural good looks and self-deprecating manner, Ms. Graham cannot handle the theatrical burden of a full-length feature.

The actress has made a career as a cinematic beauty, but her transition to genuine screen talent is perpetually stalled. Ms. Graham has always made great eye candy on film, starting with her indelible appearance as Corey Haim’s dream girl in 1988’s “License To Drive.” With memorable supporting roles in such movies as 1989’s “Drugstore Cowboy” and 1997’s “Boogie Nights,” Ms. Graham impressively kept roles as the hot high schooler for more than a decade.

But the mannerisms that added adorable quirks to her small roles have not translated in more substantial attempts. She disintegrated opposite Johnny Depp in 2001’s “From Hell” and has repeatedly struggled with emotions distinct from confusion, naïveté, and general cuteness.

Here, Ms. Graham makes Gray a cloying, ambivalent nuisance rather than an insouciant, charming blonde. The awkward coltishness that was so endearing in a young beauty looks amateurish in a woman pushing 40. As Gray rolls her eyes, paces, and bounces across the screen to approximate different emotions, the cracks in the plot and script become more and more apparent.

The supporting cast doesn’t always fare better. Molly Shannon’s Herculean efforts to wring humor from her clichéd dialogue as Gray’s sidekick are admirable but ultimately unsuccessful. Sissy Spacek is out of place as Gray’s sports-enthused therapist, and Alan Cumming’s straight cab driver who falls in love with Gray seems a failed effort at affirmative action to counter an overwhelmingly straight cast tackling homosexual themes.

Ms. Moynahan makes some headway with Charlie (though her posterior should get a costarring credit) and Mr. Cavanaugh manages to make Sam sweet and likable, despite the hastened speed of shallow dialogue.

But moments leaning toward humor and emotion are cut short by horrific set pieces that invade even the most mundane scenes. As “Gray Matters” parades various clichés across the screen, it is less the repetition than the sheer lack of humor that offends. Time spent waiting for the inevitable punch lines grows interminable as Gray’s huge iced coffee spills on a wedding dress, Mr. Cumming ends up in drag, and Sam outs Gray over the office intercom. All this and “Gray Matters” still finds time for charmless dance sequences and one of those irritating singing segments that seems a prerequisite for any romantic comedy made in the aftermath of “My Best Friend’s Wedding.”

By the time the manic Gray bemoans the loss of her civil rights as a newly minted homosexual toward the end of the film, “Gray Matters” appears designed solely to ruin the lipstick lesbian fantasy for any unfortunate heterosexual males who have been dragged into attendance.

mkeane@nysun.com