"One More Time" for troubled diva Britney Spears?

"When an artist stays off the scene for a couple of years, it is impossible to tell how much that audience has gravitated elsewhere until you put tickets on sale," Bongiovanni said.

Spears made headlines for all the wrong reasons in 2007 and early 2008 -- shaving her head, partying without panties, two hospitalizations for psychiatric checks, losing custody of her sons and giving a laughable performance at an MTV Awards show.

As the sexy young pop star who sold more than 60 million records in her heyday gave way to an erratic, disheveled divorcee, her musical and personal obituary was being written.

"Last year, it didn't seem like she would ever come out of it. Her falling apart was bigger than anybody, even Michael Jackson. I don't know if anyone in pop music has fallen that low and come back," Carpenter said.

But since February, when Spears' father Jamie took over her business and personal affairs, the singer has reunited with the manager who made her a star, won three MTV Video Music Awards, recorded her sixth studio album and relaunched her Web site.

She will mark the release of "Circus" with a November 30 TV documentary about her darkest days and an appearance, on her 27th birthday, on U.S. TV chat show "Good Morning America."

Still, Bongiovanni said it may be hard for fans to separate Spears the pop star from Spears the pop problem. "Are they coming to see you because they think a train wreck is about to happen, or because they really like your music?" he said.

(Editing by Bob Tourtellotte and Todd Eastham)