"Envy" would like to be a funnier movie. You can feel it striving, straining, almost getting there, but nearly always falling short. If movies were people, this one would probably harbor deep resentments against pictures that get effortless laughs.

The idea is a natural. The casting is good. Characters even have some nice lines -- before we're forced to get to know them, anyway. But the film quickly loses track of its comic point, getting hung up on strained shtick that, really, has nothing to do with the comedy of jealousy. A movie whose plot points depend a lot on errant arrows, "Envy" displays a remarkable knack for missing its own, rather large, thematic bull's-eye.

Ben Stiller and Jack Black play working stiffs, San Fernando Valley neighbors Tim Dingman and Nick Vanderpark. True to typecasting, Stiller's Tim is a pent-up, by-the-book type and Black's Nick is a childish, easily distracted dreamer. They both hold midlevel office jobs at a sandpaper plant. Tim, of course, gets better work evaluations than Nick.

But Nick's goofy dreams finally pay off when, with a questionable scientist associate, he invents an aerosol spray that makes doggy doo disappear. The Vapoorizer, as it's called, turns Nick into an overnight infomercial star and multimillionaire. He builds a lavish mansion on the same flight path cul-de-sac where his tract home used to be, because he wants to remain neighbors with his best pal Tim.

Which, of course, drives Tim nuts, since he pooh-poohed Nick's early offer to invest $2,000 in his silly-sounding project. Despite the entrepreneur's good-natured generosity, Nick's endless displays of conspicuous consumption can't help but rankle. The fact that Tim's avaricious wife, Debbie ("The Mummy's" Rachel Weisz), won't let him forget his mistake certainly doesn't help. For her part, Nick's wife,

Natalie ("Saturday Night Live's" Amy Poehler), decides to run for office in order to "give something back, since we have so much." Where, exactly, the Vapoorized waste goes becomes a campaign issue.Anyway, Tim's increasing vexation results in the second dead-horse joke in as many Ben Stiller movies. What "Envy" proves that "Starsky & Hutch" wisely did not is that brevity is the soul of dead-horse jokes. This conceptual nonstarter rattles on and on and on throughout the second and third acts of "Envy," and only distracts from what could have been -- and what should have been -- crueler, sharper character comedy.Black and Stiller essentially do what they usually do, not as well as they usually do it. For a brief, shining verbal jag during his character's introduction, Christopher Walken flies as the addled barfly philosopher, J- Man, who becomes Tim's partner in bungled spite and equine corpse transport. But even this marvelously mad Walken creation grows old as we realize he has no real place to go in the scenario, which is a shame for such a perfectly cast part.Director Barry Levinson can be a very funny filmmaker; "Diner," "Good Morning, Vietnam" and "Wag the Dog" are among his credits. But with a script, credited to first-timer Steve Adams (Larry David reportedly tried to salvage it), that refuses to get as nasty as it should or even stick to its main premise, the best comic minds can do little more than flail - and hope that some generous soul buys it.