"American Idol" made Simon Cowell a household name in the United States, but the prickly British music Svengali is hitting some flat notes as he tries to launch his own TV singing competition.

Cowell, 51, has been working on a U.S. version of his hit UK talent show "The X Factor" for more than 18 months. But as the clock winds down to its much-hyped debut in the fall, he is facing some last-minute challenges.

His personal pick for the judging panel -- British singer Cheryl Cole -- was reportedly dumped from the lineup, possibly because of her thick accent. She was also dropped this week from the panel of the UK version of "The X Factor".