To those Jane Fonda fans who have been eagerly awaiting her return to the screen, my condolences. It's not that she's bad in "Monster-in-Law." She seems to be having a high old time as Viola Fields, an alcoholic TV diva. Viola's lost her job to a younger woman, and publicly lost her marbles attempting to strangle a Britney Spears look-alike on camera. Now she's about to lose her only son, Kevin (Michael Vartan), to marriage. This final indignity prompts Viola to go nuclear on her prospective daughter-in-law, Charlie (Jennifer Lopez). Fonda's formidable comic chops deserve far better than the clumsy and charmless comedy concocted by novice screenwriter Anya Kochoff and director Robert Luketic.

The premise, though hardly fresh, has the makings of a ferocious black comedy. But "Monster-in-Law" is more a sour pastel. Torn between the desires to be nasty and nice, it achieves a mean-spirited blandness that makes neither psychological nor filmic sense. It's not Vartan's fault, but the object of this catfight comes off as an oblivious dolt, hardly worth tussling over. I'd cut this movie more slack if it had given me a few good belly laughs, but the best it can do--thanks largely to Wanda Sykes as Viola's sardonic assistant--is wring a few indulgent chuckles.

Except for her role in "Out of Sight," Lopez has never seemed at home in romantic comedy. Dogged and earthbound when she needs to be sprightly and spontaneous, she doesn't contrast well with Fonda--they both seem constructed out of steel. We're not surprised that Charlie proves as merciless as Viola is to her, but it's hard to delight in her revenge. The filmmakers don't even have the courage of their own misanthropy: their desperate last-minute attempt to get touchy-feely must be seen to be disbelieved.