Grade: C-

As Neil Sedaka famously observed, breaking up is hard to do, but it proves even harder to watch in this shrill, sour comedy starring current off-screen lovebirds Vince Vaughn and Jennifer Aniston. Like Rob Reiner’s 1999 misfire “The Story of Us,” Peyton Reed’s movie tries to meld seriousness and farce in dealing with a couple’s split–though in this case it’s not a husband and wife but a guy and gal who, in the modern fashion, simply live together without benefit of vows. But like that earlier picture, it’s a mess that manages to be both mirthless and dramatically tinny.

After a supposedly cute meeting of Gary Grabowski (Vaughn) and Brooke Meyers (Aniston) at a Cubs game at Wrigley Field–during which he’s such an overbearing jerk that one would presume she’d travel several thousand miles from Chicago just to be sure never to bump into him again–the movie proceeds to a Polaroid-photo credits montage showing them linking up instead, after which we’re plunked into their life together some unspecified time later. They’ve pooled their resources to buy a condo, though they still seem mismatched. She’s a trusted assistant at a tony art gallery owned by flashy diva Marilyn Dean (Judy Davis, wildly flamboyant but utterly unamusing), while he’s the gregarious tour guide of the Windy City in a small bus firm he operates with his brothers, one (Vincent D’Onofrio) officious but lovably intense and the other (Cole Hauser) a boobish would-be ladies’ man. At a family dinner that also includes Brooke’s stiff mother (Ann-Margret) and goofily glee-club brother (John Michael Higgins), as well as what appears to be either her sister or best friend (Joey Lauren Adams)–the script is never very clear about this–things finally come to a head: furious at Gary’s refusal to be of any help and his absorption in video games, Brooke tells him off and he leaves for the bar run by his gruffly honest if distinctly off-kilter best friend Johnny O (Jon Favreau).

They don’t patch things up. Though each refuses to cede to condo to the other, they brawl and bellow at one another constantly and choose to do things to irritate; she also begins dating ostentatiously (though unsuccessfully) to make him jealous. Their realtor friend (Jason Bateman) finally points out that the relationship seems broken beyond repair and that they should sell the place and end their joint misery. The remainder of the narrative takes some turns, of course, but the ultimate issue is whether the couple will (or should) overcome their difficulties and get back together. It tries for some depth in the end by opting for a bittersweet finale after the fashion of last year’s age-disparity romance “Prime,” but it has no resonance whatever.

“The Break-Up” is clumsily written overall, but what really dooms it is the fact that the lead roles are very poorly fashioned–Gary’s an obnoxious loudmouth and Brooke a dreary bundle of contradictions–and Vaughn and Aniston exacerbate the script problems by overplaying them badly (something to which Reed’s permissive direction contributes all too readily). Whatever loose charm Vaughn might have shown in other movies is lost in a character who’s little more than a caricature of the boor who’s never grown up (and ostentatiously linking that to a Polish name is more than a bit tasteless), and when he turns soft at the end, the transformation isn’t remotely credible. (Watching him, you might think of a very unfunny version of Ralph Kramden.) Aniston is slightly less flustered and jittery than she’s previously been, but not by much; and she remains a curiously annoying screen presence, perhaps more suited to outlets of television size. A few members of the supporting cast provide glimmers of amusement: Favreau brings a manic intensity to some of his shtick, and Bateman is nicely laid-back. Best of all is D’Onofrio. He was born to play Vaughn’s brother–they look so much alike–and his suppressed wildness in the part of a voluble lower-class guy trying to appear like a buttoned-down executive has a depth lacking everywhere else in the movie. But he’s underused. That, unhappily, can’t be said of Hauser, who’s all too convincingly slimy, or of the overwrought Davis, or of the one-scene Ann-Margret, or of Higgins, who’s awash in a swishy stereotype, or of Justin Long, who’s embarrassing as Dean’s Goth-goof receptionist. As for Adams, she’s so pallid and anonymous she’s barely noticeable.

There are a few nice outdoor shots of Chicago in “The Break-Up,” but otherwise Eric Edwards’ cinematography is pretty faceless, and Jon Brion’s score is bland, too. In fact, the generally mediocre production is oddly suited to a romantic comedy-drama in which there’s very little affection, too few laughs and almost no insight. This is a movie with which you’d be wise to avoid entering a relationship in the first place.