It’s easy to see why Eddie gets lost in Lila so quickly. Cute and bobbing blonde ringlets, inviting eyes on an exotic face, an awkwardly sweet woman trying to make a good first impression.

Oh, but how little Eddie really knows about her before he pops the question and gets hit, repeatedly, by a boomerang of unexpected answers.

Sex? It’s like summoning aneurysms with impossible positions and dirty direction from a lady with a cesspool mouth. Job? “Environmental researcher” becomes a pretty vague description. Deviated septum? Not the aw-shucks medical malady it seems to be. Tanning? She’ll forego sunscreen to prove a point, even if it means a face so charred it breaks out in boils and bubbles.

After supporting roles in raunchy comedies (most notably as the temptress wife to pus-faced Freakshow in Harold & Kumar Go To White Castle), Swedish-born Malin Akerman finally gets a lead-role shot in The Heartbreak Kid, a remake of Elaine May’s 1972 film.

With a fearless, unpredictable comic dedication that combines Cameron Diaz’s goony, winning smile with Anna Faris’s funny-and-frightening obsessive touches, Akerman makes the most of it. Unfortunately, most of the routine romantic comedy is made without her and with Eddie, Ben Stiller’s latest hapless schlub to disappear into the ether.

Granted, it could be an in-movie hairstyling choice, but it sure seems like playing the very same role has finally gotten to this very talented actor. There’s more salt than pepper in Eddie’s 40-year-old mane in a film from the Farrelly Brothers that surprisingly doesn’t throw in sugar with its spice.

Nine years ago, There’s Something About Mary made stars of Diaz, Stiller and these directors, who hadn’t made a bad movie since then but also not one as many people paid to see. They’ve follow a career high, 2005’s Fever Pitch, with this decided low. As two of five credited screenwriters, they’ve grafted in precious little of what they do best.

Eddie is a sporting-goods storeowner reluctant to take the bat off his shoulder when it comes to relationships. He’s the opposite of his impulsive dad (Jerry Stiller), who canoodles in Vegas hot tubs with women whose breasts he could use as a flotation device. Plus, he’s always getting dubiously doled-out advice from friend Mac (Rob Corddry), grinning and bearing his own marriage.

Eddie’s meet-cute with Lila involves a mugging and a David Bowie thong and, before long, they’re making out like sickeningly sweet lovebirds. Marrying Lila to keep her from moving to Holland for “work,” Eddie finds there’s more to her than he bargained for during a road-trip honeymoon to Cabo. (Never mind the gaps in logic that much of what astounds him is things he would have learned during a six-week courtship, especially in the bedroom given early lip locking.)

Once Lila’s sunburn confines her to the hotel room, the movie loses all its scorch. Out one night lamenting his rushed decision, Eddie falls for Miranda (Michelle Monaghan), the Farrellys’ prototypical sass-talking sexy pip who’s vacationing with her down-home family from Mississippi.

Convinced Miranda’s the one for him, Eddie plans to ditch Lila and live happily ever after with her. That it’s easier said than done is a given. But amid by-committee jokes about donkey shows, personal non-hygiene, weed euphemisms, peeing on jellyfish stings and Mexican men’s anatomy (in a role for Carlos Mencia that Paul Rodriguez must have refused), the film forgets all about Lila.

Akerman is all but absent from The Heartbreak Kid’s desperate, torturous last half-hour (which begins with a profoundly lame border-crossing montage) and from Eddie’s mind in a flash.

Lila is crazy, yes, but genuinely wants to love and please her husband — an idea the Farrellys would handle with care if they weren’t hired guns needing to pull a trigger on a career-saving hit. The real heartbreak is Akerman’s cruel cast-off, but she’s too good to not be on the rebound soon.