Fess up: You laughed when you heard the news that David Duchovny had checked himself into rehab for sex addiction.

It's funny, or seems that way, even if you know it's also a real illness and kind of sad.

That disquieting blend of raunchy-randy-ridiculous and pathetic is the heart of "Choke," a hit at the sex-starved Sundance Film Festival, but a little less than the sum of its body parts.

Sam Rockwell is perfectly cast as Victor, a sexaholic who works as an in-costume tour guide at a re-creation of an 18th-century town, a guy who lives to copulate, and who makes his real money by faking choking in restaurants. He doesn't sue the restaurant. He hits up the person who saved his life for cash. And since they've taken responsibility for him, they fork it over.

Victor does his Sex Addicts Anonymous meetings, which aren't helping. He's forever sneaking off to a closet to do the deed with a willing fellow addict. His best friend is historic- park colleague Denny (Brad William Henke), a chronic masturbator. So he's no help either.

But the funny sex and funny restaurant con jobs take a back seat to Victor's sad personal history when we meet his mom (Anjelica Huston, in great form). She's in an institution. She can't recall who he is, at times. She's given him a mystery from their past to solve.

Which takes a back seat, of course, when Victor lays eyes on the shapely doctor (Kelly Macdonald). He's so smitten by her that he can't perform, um, you know ... exercise his addiction.

Actor-director Clark Gregg (he plays a priggish fellow re-enactor) turns Chuck Palahniuk's novel into something not quite like a romp, lurching through shifts of tone, revelations about Victor's mom, his past, his changing view of himself.

"Choke" is brisk enough to be a comedy but doesn't play as one. It's too short to resolve every subject or theme it brings up - redemption, forgiveness, love. Gregg makes the movie work as a sordid sex satire but falls short in rising above that. And the many loathsome/pathetic characters make "Choke," in the end, a bit hard to swallow.