The film stars Josh Hartnett, who usually puts me off, but he is likable and effective here. His "if you squint, they will come" approach to acting actually suits his character this time around and, thank goodness, his hair is very short, sparing me from having to look at that godawful bed-hair he generally sports.

Harnett plays Matt Sullivan, a young Web site designer obsessed with Nicole (Vinessa Shaw), a girlfriend that dumped him. He is so obsessed, in fact, that when he tries to have sex with other women, he suffers black hole visions that trigger panic attacks. In desperation, he makes a vow to his brother John (Adam Trese), a would-be priest: He will abstain from anything that would provide sexual release for 40 days in honor of Lent.

This being a contemporary sex comedy, his buddies begin placing bets on how long he can last. Soon, a Web site is set up and the stakes grow higher, along with his notoriety. Of course, he meets another woman, a gorgeous, charming non-conformist named Erica (Shannyn Sossamon) and romance blooms. Note of full disclosure: I interviewed Sossamon last summer for her debut performance in "A Knight's Tale" and she playfully flirted with me. A lot. Despite being a six on the Kinsey scale, this left me as thrilled as a schoolboy, so my belief that she is destined for stardom may be prejudiced. Or maybe not. Try watching her captivating smile and tell me she isn't going to be the next Julia Roberts.

But I digress.

Shot in San Francisco, the film establishes and maintains a bright, sunny look that compliments the lightness of the storyline. While "40 Days and 40 Nights" is built on a one-joke premise, the filmmakers find a number of inventive ways to play around with the one joke. Matt's roommate uses a special light to scan his buddy's sheets, in order to ensure that "no fluids are liberated." Matt handcuffs himself to his bed to keep away from temptation, leading to some amusing physical comedy. And, as his sexual tensions reach crisis level, he begins to hallucinate, resulting in a very funny surreal flight scene.

I don't want to oversell the film, so I should remind you that, for every joke that succeeds, the flick contains a half dozen that fall flat. Still, when compared to most of the youth oriented fare released over the last few months, "40 Days and 40 Nights" shines, offering viewers 95 minutes of breezy fun.