The Switch (12A), Certified Copy (12A) (2/5, 2/5)

Well conceived, but it doesn't deliver

The Switch is one of those pantomime-horse movies in which the front half seems not to have any acquaintance with the back half. It's even got two directors, which could explain its lack of co-ordination. The front half, comprising the first 40 minutes or so, is an above-average romantic comedy that springs on its comic feet and delivers a few good jabs. Jennifer Aniston – still a likeable comedienne, still searching for a decent movie – plays Kassie, a fortyish New York single woman who's decided to take the plunge and have a baby by artificial insemination. She explains this to her longtime best friend Wally (Jason Bateman), who's so buttoned-up and neurotic that he's never been able to confess his love to her.

This scenario isn't exactly fresh – we've already had The Back-Up Plan this year – but Aniston and Bateman play off each other in their opening exchanges with a playful cattiness. "Life is in session," declares Kassie, newly emboldened by her decision. "Is that from an infomercial?" says Wally. Allan Loeb, adapting from a short story by Jeffrey Eugenides, keeps spiking this mild brew with little shots of acid. For instance, while waiting to cross at a traffic light Wally is targeted by a babbling (and mentally disturbed) man, who repeatedly calls him "a beady-eyed little man boy". The barb irks him, probably because it's true, and links up rather wittily with the story about to unfold. Kassie throws a party to celebrate her forthcoming insemination – by turkey baster – and Wally is introduced to the donor, Roland (Patrick Wilson), a toothy hunk who's married and needs the money. During a spell of paralytic drunkenness in the loo Wally contrives to switch the official seed with some of his own, though by the following day his mind's a blank.

His sperm is not so, however, and now comes the big narrative rupture. Kassie falls pregnant, leaves to live in the Midwest with her family, and returns to New York seven years later with a son, Sebastian (Thomas Robinson), who – it becomes clear to us, but not them – is Wally's progeny. Even were the resemblance not strong, the kid is a martyr to hypochondria and glumness: a natural worrywart, just like his dad. The problem for the film is not how unlikely it all is, but how much this second half unbalances the mood, tipping it away from comedy towards a fuzzy celebration of father-and-son bonding. Aniston is almost squeezed out of the frame as Wally is called in to babysit and discovers his own unsuspected paternal side. He even picks lice out of the child's head while mum's away with Roland, now divorced and eager for romance himself.

The fun of the first part resurfaces on occasion, usually when Jeff Goldblum appears to play Wally's boss, confessor and shoulder to cry on. Goldblum's lanky, swivel-eyed presence is not only a reminder of what the film might have been but also of how underused his talent still is. This actor deserves better material than the guy who's woken in the middle of the night so his friend can bellyache to him about romantic distress. And the audience deserves better, too, than ungainly plot contrivances, first of all Wally's massive memory blackout – did he really not recall that sperm switch? – and, second, his inability (lasting nearly the whole film) to be honest with the woman he loves. Yes, I know a lot of romantic narratives depend on this withholding, but there ought to be compensatory diversions while we wait it out. Bateman's pent-up longing was much less funny than his snippy awkwardness at the beginning. So what happened? It lost its funny bone, and its nerve. It lost the mentally unstable guy who insulted Jason Bateman at the traffic lights.

There's also an identity crisis bedevilling Certified Copy, though at a much more rarefied level than The Switch. The revered Iranian director Abbas Kiarostami, working for the first time outside his native country, presents a decorous two-hander that starts out intriguingly before it loses itself in conundrum. Its cast impressively matches an Oscar winner of serious accomplishment with an English opera singer who's never acted in a movie before. Juliette Binoche plays a gallery owner who attends a lecture given in a Tuscan palazzo by a British art critic (William Shimell) more warmly regarded abroad than he has ever been at home. Later, they meet up and go for a drive to a little village near Arezzo, where they happen upon a multiple marriage ceremony.

As they wander about, they shoot the breeze in a relaxed, philosophical manner. When someone mistakes them for a married couple Binoche decides to play along, and gradually sheds a different light on the encounter – not strangers meeting, after all, but perhaps a sundered pair trying to patch up their relationship. The past has suddenly entered the equation, and we seem to have gone from Before Sunset to Last Year at Marienbad. The transition is marked by a very awkward scene in a near-empty restaurant: the man, hitherto a model of suavity, turns inexplicably pompous and petulant, loudly upbraiding a waiter and batting away all of Binoche's efforts to appease him. What has gone wrong? It could be Shimell's inexperience in front of camera to blame, or a fault in the writing, but the film never quite recovers from this abrupt drop in temperature. Binoche, girlish to his churlish, is extraordinarily winning, and rather vulnerable in a private moment as she applies lipstick in a mirror. But Kiarostami's purpose remains opaque, and, beautiful though it is, the early promise evaporates in the Tuscan gloaming.