In the African American community, the barbershop has always been a vehicle tailor-made for the screen. It's where the ebb and flow of ordinary life play out on a daily basis, where men and boys gather to hash out the issues of the day -- and talk some smack.

Every snip of the scissors, every new haircut, every new client in the chair provides a fresh source of drama. Call it "As the Chair Turns." Show up at a barbershop, and you know that something's going to happen. So in retrospect it's no surprise that the "Barbershop" movie franchise did so well. It captured this strangely intimate world, with its representation of characters from all sides of the class divide, serving up laugh-out-loud moments and crackling banter with a little pathos on the side.

It worked because the humor was natural and unforced. (It didn't hurt that it had an appealing cast, starring Ice Cube as Calvin, the barbershop owner; Cedric the Entertainer as Eddie, the crotchety -- and controversial -- old barber; and the rapper Eve as Terry, a woman with an attitude problem.

Given all this, "Barbershop," the cable sitcom, should work, too. Airing tonight at 10 on Showtime, it's got an impressive behind-the-scenes crew: Ice Cube as executive producer, along with George Tillman Jr., who wrote directed and produced "Soul Food" the movie. Tillman also produced the "Barbershop" movies. (Clearly, Showtime, which enjoyed long-running success with "Soul Food," is hoping to duplicate its success.) And it's got John Ridley writing and directing. Knowing that Ridley was at the helm, we had high hopes. He's a former stand-up comic who knows his way around a screamingly funny one-liner, as well as a hardboiled crime novelist.

Then, too, "Barbershop" has the freedom of cable, with its profanity and gratuitous bare-boob shots. It's got a believable lead, with Omar Gooding (brother of Cuba Jr.) in Ice Cube's role. Veteran character actor Barry Shabaka Henley ("Collateral," "Four Brothers") plays Eddie, the grumpy old man with a fondness for testing the boundaries with offensive racial references. ("I'm going to teach you to hunt like an African. A real African with spears and bones and [expletive].")

It's got all that, and it still falls flat. And exactly why it flops is hard to suss out. Comedy, particularly when confined to the 30-minute strictures of the sitcom, has a strange alchemy. It either works or it doesn't. You either laugh or you don't. What, for example, makes HBO's often-offensive "Entourage" so hold-your-sides funny while the equally offensive "Fat Actress" comes across as a shrieking mess?

Comedy works when you don't see the strings being pulled. You laugh not just because someone says or does something outrageous, but because the outrageousness reflects real life. "Barbershop" attempts to be real, even as it's shot on a specially constructed set on a Paramount lot built to approximate a gentrifying street on the South Side of Chicago.

But its rhythms are off, from the hyperactive handheld camera to the hyper dialogue. The actors come across as Shakespearean thespians pontificating on life in Da Hood. "Running a barbershop is kinda like being at an all-you-can-eat restaurant," Calvin says in a voice-over. "Right when you think it's all out of nonsense, the chef cooks you a fresh plate of craziness."

Craziness, to be truly crazy, can't be constructed. Or at least, it can't seem constructed. And the three plot lines of the first episode are meant to echo the insanity theme. There is (1) the problem of Romadal (Dan White), an ex-con barber whom Calvin is forced to hire because of loose family ties; (2) the problem of the attitudinal Terry, who is hopping mad because she just found out her identity was stolen; and (3) the problem of Yinka (Gbenga Akinnagbe), the Nigerian barber who's got difficulties talking down and dirty in the bedroom and looks to Calvin for a little coaching, whereupon hilarity does not ensue.

They zip around and around, skipping from one jump-cut scene to another. Terry, played by the talented but miscast Toni Trucks, gets hauled off to jail because her intense gesticulating in the heat of the moment gets her mistaken for an "emotionally disturbed person."

Of course, underneath all her rage ("I grew up in foster homes. . . . Kids like me had to scrap for everything we had") lies a virgin with a heart of gold. ("Thirty-eight percent of black women 18 to 25 are virgins. My stuff is pure.") And we don't believe it for a minute. And therein lies "Barbershop's" problem. We don't believe it. And we're not laughing hard enough to forget that we don't believe it, either.

Barbershop (30 minutes) airs Sundays at 10 on Showtime, with replays Tuesdays, Thursdays and Saturdays.

Omar Gooding and Anna Brown star in Showtime's comedy series "Barbershop," premiering tonight at 10."Barbershop" denizens Isaac (John Wesley Chatham), trimming a client's hair, and Eddie (Barry Shabaka Henley).