UNIMAGINATIVELY BILLED as a hybrid of Forrest Gump and The Truman Show, this expensively-budgeted time-travelogue boasts an intriguing enough premise (two Nineties kids let loose in a Fifties TV show) as well as its fair share of highly inventive visuals, but owing to an excess of sub-Capra sentimentality and a grossly over-extended running time, it ends up spoiling much of its own impressive initial impact.

The concept is a nifty one, all the same: geeky, good-natured high-school kid David (Tobey Maguire) hates living in the Nineties and escapes by tuning into the black-and-white soap-opera Pleasantville, which depicts an idyllic/nightmarish Eisenhower-era smalltown where life is always 'swell', everybody is white and middle-class, sex and crime are not known to exist, and the men yell 'Honey, I'm home!' to their wives every night.

When the remote-control on David's telly is broken during a petty scuffle with his sister Jennifer (Reese Witherspoon), the twosome are mysteriously sucked into an episode of the TV show, from which there is no apparent escape. This is tolerable news for David, but the stuff of nightmares for his fun-loving sis, who sets about gleefully subverting the suffocating social mores of the age. Horrified by the thought of living the rest of her life in this sanitised straitjacket, the cheerfully slutty Jennifer causes consternation by seducing the captain of the college basketball team, prompting them to lose for the first time in living memory, as Pleasantville's cosy little world begins to be turned upside-down.

Nineties attitudes soon spread through the town like wildfire and corrupt the local youth, much to David's horror and Jennifer's extreme amusement. Teenagers take to shagging like rabbits at the local beauty spot, the basketball team enters its first ever slump, sheltered housewives learn how to pleasure themselves, and people suddenly discover the merits of art and literature. The onset of all this madness is signified by Technicolor creeping gradually into the monochrome: the straitlaced people remain in black-and-white, while the rule-breakers suddenly develop colour in their cheeks.

While the mix of colour and b'n'w is brilliantly realised, the actual narrative gets somewhat carried away with itself and just isn't as hilarious as it seems to think. The film manages to make a few laboured points about the inherent unhealthiness of repressed societies and the relative joys of freedom, but it hammers the point home very heavy-handedly, and I'll never know what possessed director Gary Ross to exceed the two-hour mark - at least half an hour could have been chopped with no great loss.

Best then to enjoy the acting, which is uniformly satisfying: Maguire (Ice Storm) has an appealingly sincere sort of air about him, Witherspoon is a hoot as the man-eating nymphet, William H.Macy is as priceless as the kids' ultra-stuffy father, and Joan Allen just does her usual Joan Allen thing and is perfectly at home in her role (dutiful wife, cook and home-maker).

Pleasantville turns out to be just that: pleasant, which may not quite have been the makers' intention.

Worth a look, then, but don't get too excited.