Bawdy and defiantly R-rated but also resoundingly safe and bland, "Sex Tape" gets stuck in neutral early on and fails to recover. Director Jake Kasdan, reuniting with Cameron Diaz (2014's "The Other Woman") and Jason Segel (2011's "The Muppets") following their collaboration on 2011's "Bad Teacher," has trouble finding the right tone. Its raunchy carnality appears virtually chaste, as if Kasdan and screenwriters Kate Angelo (2010's "The Back-Up Plan") and Jason Segel & Nicholas Stoller (2012's "The Five-Year Engagement") are afraid they might offend, while its familial drama is rote and homogenized. There are a handful of solid laughs sprinkled throughout, but the assumption is that bigger and better jokes are yet to come. They never do.

College sweethearts Jay (Jason Segel) and Annie Hargrove (Cameron Diaz) have always prided themselves on their active love lives, but now that they are parents with busy schedules their physical relationship has noticeably cooled. Spending the night without the kids to celebrate a potentially lucrative business deal which popular mommy blogger Annie believes she is about to be offered, the two of them decide to spice things up by recording a sex tape on Jay's iPad. This isn't some straightforward vanilla video, either, but a 3-hour, step-by-step walk-through of every position featured in "The Joy of Sex." While intending to delete the file the next day, Jay unwittingly sends it out to their friends, family and clients. Naturally mortified, they flee into the night with married friends Robby (Rob Corddry) and Tess (Ellie Kemper) to try and intercept the video from the supposedly straight-laced man who is about to buy Annie's parenting blog, toy company CEO Hank Rosenbaum (Rob Lowe).

"Sex Tape" sets itself up as a zany, "up-all-night" comedy-adventure in the tradition of 1987's endlessly entertaining "Adventures in Babysitting" and 2010's smartly funny, romantically resonant "Date Night," but then does surprisingly little with its premise. On Jay and Annie's voyage to stop their sex tape from getting out, they uninspiringly target just two destinations with a brief pit stop at Robby and Tess' home at the onset. There are too many possibilities for where this narrative could be taken, and director Jake Kasdan wastes them. Always feeling as if it is on the cusp of taking off, the film tosses in a few slyly amusing sight gags (a cactus in the background of a shot might be funnier than anything else in the movie) but seems to be saving itself for a big climactic release. The payoff, however, is thoroughly humdrum and the inevitable reveal of what is on the sex tape almost couldn't fall less flat if it tried (mild spoiler: half of it is Jay singing "Take Me Out to the Ballgame" for an uncomfortably long stretch as Annie sits across the room watching—say what?).

Cameron Diaz and Jason Segel are appealing separately and together, but their relationship as Annie and Jay too often panders to elicit an audience response. Their early days of dating in college and having sex everywhere portrays them as fun-loving verging on serial exhibitionists. When things simmer down after they wed and have two kids, the script must underline their issues and have them discuss it at length. And, when they confirm their love for each other and finally make peace with the natural ebbs and flows of their marriage, Diaz and Segel simply do not bring the resounding sense of history and pathos which, for example, Tina Fey and Steve Carrell shared in "Date Night." Credit Jay and Annie for being a couple who healthily communicate with each other, but what they are given to say usually comes off as obviously scripted.

Casting Rob Corddry (2013's "The Way Way Back") and the indefatigable Ellie Kemper (2011's "Bridesmaids") as best friends Robby and Tess is rousing in concept, but they are sadly underused. A bit where Jay and Annie find out that their longtime pals are turned on by their sex tape is ripe for comic exploration, then fizzles out immediately. By comparison, Rob Lowe (2011's "I Melt with You") is given plenty of opportunities to let loose as the unpredictably experimental Hank Rosenbaum, energetically committal to his wayward supporting turn. Possibly the best performance comes from the intriguingly confident Harrison Holzer, practically a grown man in a child's body as Robby and Tess' manipulative son Howard. His part is the only one of all the supporting players with any detectable arc, and when his motives are revealed they sympathetically inform his despicable past actions.

"Sex Tape" is a sporadically diverting but unimaginatively plotted comedy, neither as funny nor dramatically affecting as it wants to be. So preoccupied with a single set-piece at Hank's house that Annie and Jay briefly forget they haven't even begun to solve their quandary, the movie moves on to a third act where a resolution involving $15,000 holds no consequences and inadvertently gives these protagonists an aura of dishonest privilege. The treatment of nudity is additionally exploitative in the way the camera follows and lingers on unclothed backsides—those expecting more than this will be disappointed—instead of simply standing back and non-objectively observing its human subjects. Because of the juvenile way in which these scenes are shot, it immediately becomes clear that the naked body is supposed to be a comedic punchline in and of itself. For anyone older than fourteen, it isn't. There is a savvier picture to be whittled from the spare parts of "Sex Tape," and its name is "Road Trip," the far superior 2000 college romp starring Breckin Meyer, Seann William Scott and Amy Smart. This rather lame treatment of said story doesn't cut it.