GRAND PRAIRIE – Here are three clear signs of a troubled concert performance: 1. The best song on your set is a cover. 2. You're chattering and changing costumes more than singing.

3. Your background vocalist's one solo stint threatens to upstage you. That was Mariah Carey's show Thursday night before a nearly full house of adoring fans at Nokia Theatre.

Between her incessant, nonsensical talking, making the crowd wait as she slipped into four different dresses, and the poor quality of her songs these days, Carey was a mess on a platform.

The most embarrassing moment came during "Up Out My Face," the worst track from her musically lifeless new CD, Memoirs of an Imperfect Angel.

The cut is sophomoric, pure drivel disguised as contemporary R&B. I would've hated to have been one of her six male dancers trying to gyrate to that tuneless waste.

Carey seemed totally preoccupied throughout much of the gig. At one point she picked up an antique-looking chair to be used for a number, yapped as she moved it to center stage, but then put it right back where it originally was. What was that about?

Sure, "We Belong Together," "Shake It Off" and "Touch My Body" were throwaway fun. But only when she covered Diana Ross' "Love Hangover" did it sound as if Carey were singing an actual song with melody, structure and power. Is this what she's become?

I enjoyed her Dallas stop on The Emancipation of Mimi tour a few years back. She nicely combined splash with substance.

This time she lost all semblances of that. She introduced perennial protégé Trey Lorenz, and he did a splendid rendition of Michael Jackson's "Rock With You." Carey was changing, of course. Lorenz was so good she should have tried on more clothes.