FAILURE TO LAUNCH. With Matthew McConaughey, Sarah Jessica Parker, Zooey Deschanel, Terry Bradshaw. Director: Tom Dey (1:36 mins.).PG-13: Sexual content, partial nudity,language.

With so many people doing so many things wrong, it's amazing that Tom Dey's "Failure to Launch" maintains any grip on its audience's sympathy.

To the extent that it does, credit goes to its cast of likable actors - stars Matthew McConaughey and Sarah Jessica Parker, who come off as amiably dimwitted, no matter who they're playing, and supporting actress Zooey Deschanel, who keeps her edges sharp even in something as softly artificial and preposterous as this.

Wow, two paragraphs and I'm out of compliments.

"Failure to Launch" purports to be a romantic comedy inspired by the current trend of adult men staying rooted in their parents' homes, enjoying the amenities of a B&B while carrying on carefree bachelorhoods outside.

This trend has yet to appear on my cultural radar but, taking the filmmakers at their word, I can't imagine that the movie's plot will resonate among real bachelors and bachelorettes.

McConaughey plays one of these cavalier home boys, a 35-year-old yacht salesman, Porsche owner and amoral skirt chaser named Trip. He invites women aboard his out-of-town clients' yachts, pretending to be the owner, then wines, dines and beds them.

When they give him that dreamy look of a wanna-be wife, he brings them home, claiming his parents' house as his own, and - by prearrangement - has his bumptious father (Terry Bradshaw) interrupt them in the sack.

Nothing, Trip assures us, cools a chick off quicker than being caught with her pants down by her lover's father. I don't know, throwing her out the window would be quicker - and more humane.

To his parents' credit, they find Trip's behavior repulsive, but then so is their solution: They hire an interventionist named Paula (Parker), who specializes in getting these "adult-escents" to fall in love with her and leave home, presumably to have their black hearts broken.

The plot synopsis sounds less like sitcom than sick-com: A womanizer has the tables turned on him when he falls in love with, essentially, a prostitute whose services are being paid for by parents who don't have the decency to ask him to leave.

When the revelations start flying, whose hurt feelings are we supposed to care about?

"Failure to Launch" sounds like really bad Oscar Wilde, but it's not that good. You are not supposed to dislike anybody here. By the happy faces worn by McConaughey and Parker, you know Trip and Paula don't see themselves as ill-behaved, and in case you do, details about painful events in their pasts are provided as excuses.

One thing we can all agree on: They deserve each other.

The small pleasures of the film are in the performance of Deschanel, who is truly funny as Parker's cynical roommate, a lovelorn scowler whose current life goal is to murder the chirping mockingbird keeping her awake at night.

And though the scenes where Trip and his two best friends - also parasitic live-at-homes - have their sports outings punctuated by biting animals are meaningless digressions, they are passably amusing.

Finally, please pay special attention to the PG-13 rating, which warns of "partial nudity." The reference is to the butt-ugly backside of Bradshaw, the former Pittsburgh Steelers quarterback, and it is on full-screen display for so long you may forget that the film's major offense is its own failure to launch.

Maybe that's its purpose.