Like a boy who’s overslept on the first day of school, Miles Raymond (Paul Giamatti) wakes up in a panic. He’s late in picking up Jack (Thomas Hayden Church), his best friend, for a week-long bachelor adventure in wine country. He’s manic – for about a minute. Then writer-director Alexander Payne (“Election,” “About Schmidt”) gets the first of many laughs with a quick montage of Miles taking it easy in the shower, on the commode, at a cafe where he orders a triple espresso, the New York Times, and a spinach croissant.

From the start, “Sideways” is a richly funny movie, cultivating comedy from a thick mulch of character. (If a movie could be certified organic, this is it.) But the humor is complex, bittersweet, with more than a hint of something sour. Resentment throbs like a bruise under the sunny skin of “Sideways,” a buddy flick laced with hostility, a road movie that sidetracks to abrupt dead ends.

As the buddies head north to the Santa Ynez Valley in a red convertible Saab, we learn that Miles teaches high school English and is the author of a novel, more than 700 pages long, that “evolves, or devolves, into a Robbe-Grillet mystery.” Later, we will not be surprised to find out that Conundrum, the last of the small-press imprints to show an interest, has chosen to pass. Miles never recovered from his divorce, and his connoisseurship of wine possibly dovetails with alcoholism.

Jack, a former soap star turned voice-over hack who is about to marry up, is everything Miles is not: cheery, confident, laid-back, sociable. With his broad, television-handsome features and expansive goodwill, he’s the perfect foil for Miles, the ultimate middle-aged disappointment. Jack vows to get both of them laid; but if Miles persists on getting too drunk and “going to dark side,” he’s on his own.

After swinging by Oxnard to wish his mother happy birthday and steal several hundred dollars from her sock drawer, Miles takes Jack to his first wine tasting. Observe the color, sample with your nose, then taste: citrus, strawberry, and passion fruit, a whiff of asparagus, and a flutter of nutty cheese. Miles darts a look: “Are you chewing gum?”

They arrive at Los Olivos and settle into the Windmill Inn. At dinner, Jack pressures Miles to seduce Maya (Virginia Madsen), a waitress he knows from previous trips. The next day they meet the beautiful, flirtatious Stephanie (Sandra Oh), and purchase several cases from her winery. Everyone pairs up at dinner, then pairs off for affairs (carnal for Jack, chaste for Miles). Much wine is uncorked, releasing a flow of insecurity – at least for the men.

“Sideways” might be summarized as a movie about what happens when a midlife crisis collides into the perfect woman. Maya and Stephanie are marvelous creations, beautifully performed by two splendid actresses; yet they’re marvelous and beautiful and splendid to the point of being over-idealized. This movie is about men, and Mr. Payne is as good as any contemporary American director on men’s fears, failures, and friendships.

Mr. Payne’s screenplay (co-written, as usual, with Jim Taylor) stirs pain, hilarity, and pathos into something effortless, crystal-clear – Miles would begin his praise by deeming it exceptionally “quaffable.” If “Election” felt both sharper and less controlled, “Sideways” in all ways improves on the similar road trip taken by “About Schmidt.” Mr. Payne’s touch is unobtrusively exact, perfectly fit to the shape of the screenplay and space of the actors. Mr. Giamatti fills up the most room, bringing his nebbish personae to a nearly insufferable apotheosis, solidly building on his over praised turn in “American Splendor.”

But Mr. Church is the real discovery here, worthy recipient of every Best Supporting Actor prize he’ll pick up at the end of the year. The smartest move in “Sideways” is the slow undermining of Jack’s goofy stud personae, the gradual exposure of his helplessness. The bad vibes in Mr. Payne’s work upset his detractors, who misread honesty as condescension. But it’s the trace of despair in “Sideways” that gives it body. The film is full, delicious comedy, stuff to get drunk on, then cry.

***

“Undertow” underwhelms. The director is David Gordon Green, a big talent not yet 30, whose previous films were “George Washington” and “All The Real Girls.”

His debut announced an impossibly precocious Malick-out-of-Carolina: woozy CinemaScope compositions, free-floating narrative drift, barbituate voiceover. Passing this same bag of tricks to a romance picture, “All the Real Girls” flirted with disaster but touched a real nerve – it was slightly ridiculous and absolutely sincere. Now Terrence Malick himself has stepped forward to produce “Undertow,” a gothic thriller set in the swamps, hog farms, and byways of deepest Georgia. As if made timid by the presence of his master, Mr. Green’s most extravagant Malickisms have been inhibited – and so has his imagination.

John (Dermot Mulroney) looks after his two boys, Chris (Jamie Bell, aka “Billy Elliot”) and Tim (Devon Alan). Chris is deep in the rebellious angst of puberty; Tim eats paint and mud. Life is more or less fine, if incredibly dirty, until John’s brother Deel (Josh Lucas) shows up. This being the South, there’s buckets of bad blood between brothers, and more than one family secret to discover. Halfway into the film, Chris and Tim are on the road, fleeing from Deel, a sock full of gold in their knapsack.

Part “Night of the Hunter,” part Boy’s Own adventure, “Undertow” never moves with gravity; it’s all lyric crest and cliche swell. Mr. Bell is striking, Mr. Alan compelling, but they never really inhabit the story at hand; they might just as well be posing in a “George Washington” tableaux.

They’re most fully characters when they build a fort in a junkyard: a bit of windshield, some hubcaps, a nicely done platform. That’s “Undertow,” a tricky pile of cast-off parts, neatly handmade, but rickety.