Whenever more than two movies set in the Old West come out, reflexive discussions about the rebirth of the Western sprout up like mining towns and just as quickly fade away. It certainly happened last fall, when “The Assassination of Jesse James by the Coward Robert Ford,” “3:10 to Yuma,” and “There Will Be Blood” offered three worthwhile entries in the genre. A year later, that Western surge is still too fresh in the collective mind for this year’s fall previews to make much fuss over Ed Harris’s directorial attempt in the genre, “Appaloosa,” which sidles up to theaters today. But the movie’s problems — over-optimistic casting, clumsy direction, general inertia — justify a low profile.

Mr. Harris stars as Virgil Cole, a roving lawman who becomes tasked with liberating the small town of Appaloosa from a bullying rancher named Randall Bragg (Jeremy Irons, in one of the film’s two casting missteps). Everett Hitch (Viggo Mortensen) is Virgil’s rifle-toting right-hand man, while Bragg is a brazen taker of horses, women, and lives. Finally, reflecting a demanding moment in the Old West when there was simply no time for two syllables in a surname, Allison French (Renée Zellweger, the other casting mishap) is the woman who comes between Virgil and his work.

Virgil and the nattily attired Everett make quick work of Bragg’s gang, which they stop from raisin’ hell and urinatin’ on saloon floors. Bragg himself is a tougher customer; it was his merciless killing of the three preceding law enforcers that spurred the town’s cowed aldermen to reach out to Virgil in the first place. In an oddly modern-sounding legal contract, Virgil is given explicit carte blanche that officially makes his way the only alternative to the highway.

But in “Appaloosa,” the dynamic that emerges is not the way of the gun but the allure of settling down. Virgil and Ms. French, who is some kind of traveling piano teacher, take a shine to each other and commission a house. Everett is philosophical about the matter, maintaining an unruffled array of angular poses — he even notifies Virgil when Allison makes an explicable pass at him. The real trouble comes when Bragg is put on trial and jailed before predictably busting out and making a hostage of Ms. French.

For a while, “Appaloosa” intrigues by not pressing hard on its various possibilities. Eventually, though, this state of limbo leaves the movie stalled on the launching pad. Messrs. Harris and Mortensen, who last starred in opposing roles in David Cronenberg’s “A History of Violence,” do convey an admirably unshowy companionship, but if the two actors seem plausible inhabitants of the milieu, Ms. Zellweger and Mr. Irons all too easily take the viewer out of their world.

As scripted by Mr. Harris and his co-writer, Robert Knott, the slapdash character of Allison French clearly requires an actress who can fill in some considerable blanks or supply some sort of singularity. Ms. Zellweger does not, and on the evidence of an ever-more-constrained repertoire of dramatic techniques, perhaps cannot. Mr. Irons is unshaven and suspicious-looking, but still resembles a dissolute Londoner on a transatlantic flight more than a rangy American landowner who knows his way around a spittoon.

“Appaloosa,” which is adapted from a novel by the mystery writer Robert Parker, is shot by Mr. Harris (in his second foray behind the camera, the first being 2000’s “Pollock”) with some plodding tendencies, including frontal framing that stops action scenes dead and a uniformity that hampers sensitive moments. “Feelings get you killed,” one character warns, but they shouldn’t do the same to a movie. “Appaloosa” at least stays loose with its humor throughout, especially in regard to Everett’s buttoned-up awkwardness about love.

The story lingers in some interesting, uncharted territory after the requisite shoot-out that ordinarily might lower the curtain. Perhaps not surprisingly, that’s also when Mr. Mortensen’s character enters the spotlight more fully; he’s the sort of actor who can make a scene more interesting with something as simple as a shift of his weight. And in a movie with a respectable level of production detail, one gets the feeling that he chose his own exquisite facial hair: His mustache and goatee give even Daniel Plainview of “There Will Be Blood” a run for his money.