LL Cool J quits Janet Jackson tour

Rapper had scheduling conflicts, publicist says

NEW YORK -- In another setback on her "Rock Witchu" tour, Janet Jackson has lost her opening act: LL Cool J.

The rapper's publicity firm announced Monday that he has dropped out as the opener for Jackson because of scheduling conflicts.

It's the latest problem on Jackson's tour, her first North American outing in seven years. The singer was forced to cancel a string of earlier concerts because of a bout of migraine-associated vertigo. She recently resumed while being treated for the illness, which is characterized by dizziness, imbalance and other symptoms.

Jackson's upcoming shows are Tuesday in Auburn Hills, Mich., and Saturday in New York. She is expected to announce more dates.