Andy Sitzer is a nice guy, so nice in fact that his colleagues are convinced there's something wrong with him. But instead of being the serial killer they all feared, they discover he's the most unusual of things; a forty year-old virgin. Once his friends uncover his secret, they set about solving his little "problem" as quickly as possible, hiding away his huge collection of action figures, dressing him up nicely and setting him up with all manner of unsuitable women.

Director Judd Apatow's grounding in television shines through in this movie with his refreshing attitude to character development in comedy, allowing the protagonists to develop at their own rate instead of wading straight in with a bunch of knob gags. Still, when your film is called "The 40 Year-Old Virgin" the audience already knows the punch-line. Though there are elements of gross-out humour, this is essentially a character piece with lots of jokes thrown in. Apatow clearly feels for his main character and leading man, riffing on his situation without laughing at the man, allowing him to be a sympathetic character. The director is at home with many types of comedy, from prolonged character turns to one-liners and slapstick, often in the same scene. But he also knows how to frame them, making them feel like an escalation of a situation rather than a succession of jokes. Though you're always rooting for a happy ending for the unfortunate Andy, it never feels like a predictable outcome thanks to the comedy of errors that occurs. To be fair, it isn't as laugh-a-minute as I'd been led to believe, but there's still plenty here to raise a smile if not a chuckle and the cumulative effect is pretty good. Plus the musical finale is one of the single funniest sequences I've seen at the cinema for a long time, virtually leaving me prostrate with mirth. If there's anything that typifies Apatow's directorial style besides its crisp visuals is his reliance on montages that are applied to Andy's sexual history, his bonding rituals with workmates, a speed-dating scene and Andy's strange hobbies. Though it could feel over-used, the montages are so well observed it's difficult to dislike them.

The screenplay by Apatow and star Steve Carell marries broad strokes of humour with a relatively warm romance between Andy and Trish that works because it's against all the odds though not so outlandish that it seems unfeasible. Things are wound up slowly - showing Andy's everyday life before going for the big reveal and then placing him in a rapid succession of uncomfortable situations (from speed-dating to taking his girlfriend's teenage daughter to a family planning clinic). Though pitched as a sex comedy, the underlying message is rather romantic in that love conquers all. Sex may be Andy's aim but though he goes through hell, he learns that it isn't the be-all and end-all. The characters often border on archetypes but are deftly sketched, making more of them than the comic plot devices they could have been. Sure they all have sexual hang-ups of their own (strange peccadilloes, obsession with an ex-girlfriend and commitment phobia), but they have enough meat on their bones to work as characters rather than gags. The humour covers everything from knob jokes to sustained character comedy. It is often funny, occasionally sharp, sometimes wince-inducing and not afraid of being in poor taste. It's a scattershot approach that works surprisingly well, but its broad spectrum may not be everyone's cup of tea. Even if you aren't awestruck overall, there is likely to be something to make you smile. Occasionally the writers don't know when to stop (like in the "You know how I know you're gay?" conversation) and the gags outlive their natural end, but the pacing is otherwise favourable. You can tell the screenplay was co-written by an actor because it gives even peripheral characters lines they can really chew on and situation in which everyone looks funny.

I've liked Steve Carell ever since he played simpleton Brick in "Anchorman". He's blessed with a sympathetically bland face and excellent comic timing that work marvellously in conjunction with his talent for sustaining a character. As Andy he is both endearing and unfortunate; an unprepossessingly dull man with all the social skills of Dustin Hoffman's "Rain Man". It's not so much the character but how he reacts to the increasingly ludicrous situations he finds himself in that is funny (like when he's locked in a room with a big screen TV showing nothing but porn). But he's more than a stooge for the copious number of jokes, keeping the audience rooting for throughout and making the script really work for him. He creates a sense of palpable embarrassment that pervades his entire performance, without deriding the character. Besides, you have to admire a man willing to have his extremely hairy chest waxed for real on film for everyone else's entertainment.

Fellow "Anchorman" alumnus Paul Rudd seems to have found his niche as secondary comic support. He puts in a decent turn as ex-obsessed David; deadpan, pseudo-spiritual and clearly bi-polar. Flashing from warm heart-to-hearts with Andy to rants about his former girlfriend, he's an acidic foil to Carell's nice guy. Even further away spiritually than Andy is his workmate Jay played with relish by Romany Malco. His character is the hardest to believe because of his horribly outmoded attitude to women and his increasingly foul mouth. However, it works in the context of the film because he is the most inappropriate mentor Andy could have. Plus he's allowed to redeem himself as the film progresses, becoming more human and likeable. Seth Rogan gets the thin end of the supporting character wedge as stoned warehouseman Cal. This is mainly because he exists as a plot device whose sole function is to tutor Andy in how to talk to women.

Catherine Keener shows her lighter side as Trish, the object of Andy's affections. Managing to be warm and sarcastic, she plays it straight as a very grown-up, unapologetically strong woman with plenty of her own neuroses. She's also damned sexy, flying the flag for older women. It's easy to see why Andy is both attracted to and terrified by her and why the men in this film have such problems understanding women.

The soundtrack varies between playing it straight and milking laughs from the content of its songs. So Andy's self-seduction is accompanied by Lionel Richie's "Hello" and his date's drunken driving by Missy Elliott's "Get Ur Freak On". Much of the rest is backed-up by an abundance of 1980s' soft rock standards that though appropriate to the main character's age often feels like a concession to the current fetish for all things from the power-dressed decade. The most amusing use of music is in the full-on finale played out to "The Age of Aquarius" that is so funny because it is at such odds to the tone of the rest of the movie. The score proves composer Lyle Workman workmanlike by nature. There's a bit of indie rock here and a touch of funky Hammond organ there, but it doesn't really add another dimension to the film or even shore the content. It's pleasant enough but not exactly mind-blowing.

If you'll forgive the pun "The 40 Year-Old Virgin" is a surprisingly soft-centred sex comedy with more gags than your average blockbuster. However for my money it has been over-hyped and occasional concessions to poor taste bring down the otherwise sparkling writing. There are a number of well-accomplished performances (Carell's in particular shows a star in the ascendant) that keep it going and a fantastically odd ending that makes up for many of its shortcomings. Watch it if you're in a good mood to start with and fancy a few laughs at someone else expense, but don't expect it to linger long in your brain once it's ended.