Singer Ashlee Simpson (search) gets another chance to sing live — perhaps — on national television Monday after walking off "Saturday Night Live" in a does-she-or-doesn't-she lip-synch moment.

Simpson is scheduled to perform in Las Vegas for NBC's "Radio Music Awards," (search) scheduled to be televised at 9 p.m. ET.

The 19-year-old was the talk of the Internet after Saturday's show.

Her record company blamed a computer glitch and she blamed her band, which cut off her planned performance of the song "Autobiography" (search) on the network comedy show.

Simpson had performed her hit single "Pieces of Me" without incident earlier in the show. When she came back a second time, her band started playing and the first lines of her singing "Pieces of Me" could be heard again.

She was holding her microphone at her waist at the time. Simpson looked momentarily confused as the band plowed ahead with the song and the vocal was quickly silenced.

Simpson made some exaggerated hopping dance moves, then walked off the stage 35 seconds into the performance. NBC quickly cut to a commercial.

"What can I say?" guest host Jude Law (search) said with Simpson standing next to him at the end of the show. "Live TV."

"Exactly," Simpson said. "I feel so bad. My band started playing the wrong song. I didn't know what to do so I thought I'd do a hoe-down."

Her record company, Geffen Records, said that instead of some pretaped electronic percussion, the recording of "Pieces of Me" started.

But it sounded suspiciously like a guide vocal that's a common — although almost always unspoken — concert aid. Either the singer "lip synchs" by mouthing words to a backing tape or has a live microphone and sings along to the tape, making the voice sound more powerful than it is.

Simpson's walk-off joins the lore of other unexpected music moments on "SNL": Elvis Costello (search) stopping and changing songs on live TV, and Sinead O'Connor tearing up a picture of the pope.