Less than two weeks before the planned Jan. 3 release of her sophomore Columbia album, "Pretty Little Head," singer/songwriter Nellie McKay has voluntarily left the label, sources tell Billboard.com. At deadline, the fate of the album is unknown; a spokesperson for the artist had no comment and McKay could not be reached.

The parties apparently reached an impasse over the length of the project. McKay insisted the label release her 23-song, 65-minute version, while Columbia sent out promotional copies of a 16-song, 48-minute album. Reviews of the set, which features guest appearances from Cyndi Lauper and k.d. lang, have already begun appearing in music magazines.

At recent shows, McKay had given out the personal email address of Columbia chairman Will Botwin from the stage, encouraging fans to press for the release of the longer version of the album. Botwin left the company earlier this month.

A concert DVD, "Live at the Independent," was also scheduled to hit stores on Jan. 3 but Billboard.com understands that release is also on hold for the time being.

"Pretty Little Head" is the follow-up to McKay's acclaimed 2004 double-disc debut, "Get Away From Me," which reached No. 1 on Billboard's Heatseekers chart and has sold more than 104,000 copies in the United States, according to Nielsen SoundScan.

The lone upcoming show on McKay's schedule is Jan. 22 at the Birchmere in Alexandria, Va. From there, she will move on to her Broadway debut as Polly Peachum in a new version of Kurt Weill and Bertolt Brecht's "The Threepenny Opera." Previews of the show begin March 24, while the opening is set for April 20. Lauper recently joined the cast of the production, replacing "Sopranos" star Edie Falco.