Yeah Yeah Yeahs, Forum, London

The heady mix of hype and talent bubbling around the Yeah Yeah Yeahs, from New York, on this one-off return to London should have made for an explosive night. But the plug is pulled on the crowd's pent-up emotions within minutes of its start. As her band play the jerky new single, "Pin", the singer, Karen O, falls to her hands and knees, crawling suggestively across the stage, so exciting some fans that they seem ready to climb up after her. A security phalanx bulls forward, crowd and idol never touch, and a sense of distance dulls everyone.

O's stage antics and clothes - custom-made ripped and shredded dresses and fishnets, half-falling off as she prances, shrieks and cartwheels through songs - are the Yeah Yeah Yeahs' most infamous aspects to date. Photos of their riotous shows have been a more convincing ad for them than their debut album, Fever to Tell, which draws on more awkward elements of New York's punk past than The Strokes' music, takes longer to like, and, though, good, isn't worth its gushing hype. Perhaps as a result, it's hardly flying off the shelves.

Live, the Yeah Yeah Yeahs are more powerful, Nick Zinner's rasping guitar punching to the top of a rumbling sound that frequently falls apart, when not slumping into a "Sister Ray"-like drone. The complicated disjointedness keeps them interesting and also, perhaps, helps to explain their disappointing sales. But on stage they are anyway just a thundering backdrop to their singer.

O is dressed in a pink ball-gown tonight, recalling the dress blown up around Marilyn Monroe's waist in The Seven Year Itch, and she is soon hitching it up to her thigh. But, even as she thrusts her crotch at us, her act is a million miles from pure male fantasy, or the faux testosterone of the last iconic punk front woman, Courtney Love. Throwing herself giddily around, gurning and flopping her head like a doll and naughtily flashing her knickers, she is reminiscent of a drunk nine-year-old, immaturely transported by new sensations. When she dribbles beer down her front, she could be all of 15. With her pleasure in new, interesting clothes, the parodic picture of excited girlhood is complete. No wonder she inspires female wannabes, who have at last been given an equivalent to the surly teenage kicks of male punk heroes.

Even when O chews open a fluffy toy rabbit, though, the feral spirit of Johnny Rotten isn't here. The drunk nerves behind O's act are too obvious, as is her niceness: one song is dedicated "to my fucking parents". Nor is this an exciting, transformative show. That would need the grabbing closeness that the bouncers banned. Instead, it's effective punk pantomime, with O as the dizzy dame.