Love at first sight can be thrilling, but it can very very inconvenient when it happens to a bride who is walking down the aisle at the time. Especially if the loved-at-first-sight object of affection is another woman.

Rachel (Piper Perabo) is about to get married to Heck (Matthew Goode). But then she sees Luce (Lena Headey), the florist, and the connection is immediate and irreversible. And so we get the usual do-si-do until everyone lives happily ever after.

Romantic comedies take place between the meet (usually “cute”) and the happily ever after.

In between, the movie’s job is to get us rooting for the couple while it comes up with entertaining ways to keep them apart long enough for us to finish our popcorn and well enough that we feel that they’ve earned that happy ending.

Two traditional rom-com set-ups are immediate conflict (Bringing Up Baby, where a character summarizes the meta-theme of romantic comedies: “The love impulse in men frequently reveals itself in terms of conflict.”) and what I call the “boy who cried wolf” theme, where someone tells a lie and gets deeper and deeper, afraid to tell the truth to the trusting soul he/she now adores.

The first catgory (The African Queen, My Fair Lady, It Happened One Night, Moonstruck, When Harry Met Sally) depicts the sparks and the chemistry while the second (Some Like it Hot, Roman Holiday, Guys and Dolls) is a metaphor for the conflicts we feel as we reach for intimacy and authenticity but resist the vulnerability. Some set-ups, like The Taming of the Shrew combine the two.

In dramas, too, there has to be something keeping the couple apart. We often see the barriers of family (West Side Story, Slpendor in the Grass) or history (Casablanca, The English Patient). But romantic comedies are usually about overcoming initial dislike or becoming more honest.

This film’s trendy twist is that the heroine leaves the man she thought she loved for the female florist who decorated her wedding. But the real departure is not the gender of the loved one — it is the violation of the “almost” rule of comedy. Brides are supposed to run away just before the “I now pronounce.” In this film, she goes through with the wedding, one of several reasons that keep it from achieving the spirit of lightness and possibility that are essential for any romantic comedy, no matter what the gender of the couple. Despite some clever dialogue and the sympathy it creates for its characters, the movie’s essential mis-handling of its tone keeps it from working. The problem is not the same-sex romance; it is the disconnect between the lightness of atmosphere and the seriousness of a heart-breaking betrayal. If the movie is going to be named for a bubble-gummy 1960’s pop song, it had better stay just at the “almost” edge. Once this one goes over, giving us a groom who does not deserve to be treated this way, the movie just can’t recover.

Parents should know that the subject of this movie is a previously heterosexual woman who falls in love with another woman. There are sexual references and non-explicit situations, including same-sex kisses and references to watching porn (with some spicy titles) and to a man who likes sleeping with lots of women and propositions many of them. All of this is played for humor. Characters use some strong and crude language. There are references to depression and some unpleasant family situations. Characters drink alcohol.

Families who watch this movie should talk about what the parents of the characters most wanted for their children.

Families who enjoy this movie will also enjoy Four Weddings and a Funeral and Love, Actually.

They are so afraid we won’t get the point that this movie has our heroine literally letting down her hair, literally putting some color into her beige world, and — in case we still don’t get it — literally having her undernourished garden bloom. And yet, we go with it, thanks to a luminous performance by Sanaa Lathan, who has us rooting for her from the beginning.

She plays Kenya, a very successful investment banker who spends Valentine’s Day with her three best girlfriends — a judge, a doctor, and a lawyer — all wishing they could find love.

Kenya thinks she knows what she wants. She has a list. But love has a way of teaching us — often with great discomfort — that we don’t always know what we want. And ever since Jane Austen, romantic comedies are there to let us enjoy that lesson because it is happening to someone else.

Kenya agrees to go on a blind date, but she is so unsettled when she discovers that he is white she abruptly tells him it can’t work and walks out. Later, when she admires a friend’s garden, it turns out he was the landscape architect and she hires him to — metaphor alert — create a beautiful oasis in the neglected back yard of her new house.

Not only is Brian (Simon Baker) missing the attributes on Kenya’s list, he has a few items on her “no” list — like a dog, and a job where he doesn’t have to wear a tie. But he is kind and smart and considerate, and he knows how to make things bloom. He likes Kenya very, very much. And the her that he likes is a her she’d like to be more of the time — maybe.

Kenya has devoted all of her energy to being what her parents wanted her to be. When Brian urges her to remove her long, straight, glossy hair weave, her aristocratic and a bit pretentious mother wails, “But it was your crowning glory!” Kenya gently reminds her that it wasn’t really hers.

It was her mother’s opinion that strong, bright colors are for children, so everything in Kenya’s new house is beige. Soon Brian has her dipping a paint brush into deep, rich colors, and, of course, splashing it around a little, too.

Kenya wants to think of it as a fling, a momentary Lady Chatterly detour from the path of searching for the IBM (Ideal Black Man). That way, she does not have to think about what her parents or her friends think or about her list (which is a reflection of her parents and her friends). And if he’s just a fling, she does not have to think about her own prejudices. Until an IBM (Blair Underwood) shows up, a handsome and successful lawyer who wants commitment. He is everything she ever wanted. Isn’t he?

This is a glossy romantic comedy with an appealing heroine and some bright dialogue and the theme of racial differences, with the black family highly educated and affluent referring to the landscape architect as “the help” adds a little freshness to a traditional when-will-she-realize-he’s-her-true-love storyline. Another bonus is a superb soundtrack by former Prince-ites Wendy and Lisa. If the over-perfect devotion of the boyfriend makes it less of a date movie than a chick flick (he’s not allowed some sympathy for a bad day?), the sweetness of the relationship and the tartness of the wisecracks around it keep it, if not something new, at least, something welcome.

Parents should know that this movie has some strong sexual references for a PG-13 and some non-explicit sexual situations. Characters drink (scenes in a bar) and use some strong language. A strength of the movie is its portrayal of a loving and devoted inter-racial relationship.

Families who see this movie should talk about why it was so hard for Kenya to be honest with herself about what she wanted.

Families who enjoy this movie will also enjoy Love and Basketball and Brown Sugar (also starring Lathan), Annie Hall, and Before Sunrise.