LeAnn Rimes' rough year has included a stint in rehab for "anxiety and stress" (or maybe not), a breakdown on E! regarding her first marriage (which ended in her cheating with actor Eddie Cibrian, who left The Real Housewives of Beverly Hills' Brandi Glanville for Rimes) and an accusation from Glanville that Rimes is addicted to laxatives ("LeAnn has a severe eating disorder. She has [a laxative] in every purse," is the poetic way in which Glanville informed the world).

And now there's this performance with X Factor finalist Carly Rose Sonenclar, which aired on last night's show. It was, in a word, a disaster. To call Rimes' vocal performance "pitchy" on this duet version of her signature song, "How Do I Live," would be like calling her hair "tussled." She missed more notes than she hit, sing-babbled inarticulately and started out nearly stumbling, which she vocally telegraphed in what sounded like a hiccup. Maybe she had an off night, or maybe she's losing the one thing she had left: that phenomenal, acrobatic voice of hers.

X Factor judge Britney Spears described the performance as "shockingly amazing." Well, she got the "shocking" part right, at least.

For her part, Rimes is carrying on her merry way, if her sole post-performance tweet is to be trusted:

Update: Rimes tells TMZ she wasn't impaired, and has opted to throw her duet partner under the bus. "I was trying to help this 13-year-old girl who was having some trouble with the song," she says, apparently oblivious to her status as the one with the problem.