The high-concept comedies spawned by "The 40-Year-Old Virgin" need to start using birth control.

Judd Apatow’s landmark film rightfully ushered in a new era in comedy, but it has also inspired a now sizable cottage industry of thin movies ("The Hangover," "The Five-Year Engagement," "Bad Teacher," "Horrible Bosses," "The Other Woman") with concepts boasting good titles but shallow stories.

Of these, only one ("The Five-Year Engagement") had Apatow’s imprimatur. He and his cohorts have mostly moved on to telling stories about various seminal chapters of life — childbirth ("Knocked Up"), high school graduation ("Superbad"), young parenthood ("Neighbors"), 30s singledom ("Bridesmaids"), middle age ("This Is 40") — and many of these make up some of the best comedies of the past decade.

‘SEX TAPE’ Rated: R Opens Friday

"Sex Tape," however, belongs to the former group and it marks a low point despite coming from several Apatow acolytes. It’s directed by Jake Kasdan, a consulting producer on "Freaks and Geeks" who went on to direct "Bad Teacher." "Sex Tape" reteams that film’s lead duo, Jason Segel (a near constant in Apatow-land) and Cameron Diaz, the always game, wide-smiling muse for what’s now been several generations of comedy.

A screwball that takes its genre literally, "Sex Tape" is about a West L.A. married couple, Annie (Diaz) and Jay (Segel), trying to reawaken their love life after years of marriage and two kids. After failed attempts with double-knotted roller skates and new venues like the kitchen floor ("I can see my to-do list," Annie says), they settle on making a pornographic movie for themselves that tours through the positions of "The Joy of Sex."

In the first of many outlandish plot twists, Jay hands out his old iPads like party favors at a get-together of friends and family. Hours afterward, an anonymous text makes him realize that each iPad has their video stored on it, due to a syncing app he favors. The technological premise has already been debunked, but that’s only a minor problem for the movie.

While this setup could have gone somewhere interesting (shouldn’t the video go viral?), the screenplay by Segel, his writer partners Nicholas Stoller (director of the far superior and somewhat similarly themed "Neighbors") and Kate Angelo bizarrely settles for a suburban nighttime odyssey wherein Jay and Annie try to take back the iPads.

This includes a stop at their friends’ house, a similar couple played by Ellie Kemper and Rob Corddry; a visit to Annie’s prospective new boss, a family website CEO who wants to buy her blog (Rob Lowe); and a Los Angeles porn warehouse (with a memorable uncredited cameo by Jack Black).

In short, it’s a PG plot for an X-rated story. The movie is so desperate for laughs that it resorts to gags like a chasing dog that can open doors and Lowe’s family guru doing cocaine lines with Slayer pounding. Segel’s gratuitous full-frontal nudity in "Forgetting Sarah Marshall" was far funnier and more surprising than anything in "Sex Tape." He has slimmed down notably, seemingly going for a more grown-up (and, alas, less funny) screen presence.

To its credit, there’s a lightness to the film and the performers are uniformly likable. When Kemper and Corddry appear (their couple yearns to see the video as their own turn-on), you wish the movie would stick with them and their nervous energy.

"Sex Tape" tries to somehow bridge the gap between the traditional romantic comedy and today’s porn-addled digital world. It’s a valiant effort, and there is something — though only very little — of Cary Grant’s scampering in "Bringing Up Baby" to Segel’s mishaps around the CEO’s mansion. But "Sex Tape" doesn’t sync.

Jake Coyle, Associated Press