There's some more info at "FOr Annie Leibovitz, a Fuzzy Financial Picture" (NYT - July 31, 2009) www.nytimes.com
What did she need the $24 million loan for? From the above referenced article:
Friends and colleagues said that despite her many successes, Ms. Leibovitz has been shadowed by a long history of less than careful financial dealings. Public records show that in the last two years, Ms. Leibovitz has faced tax liens of $1.4 million and two lawsuits claiming that she has not paid more than $700,000 in bills for photography services.
"The mind that can take these extraordinary pictures is not necessarily the same mind that is a perfect money manager," said Graydon Carter, the editor of Vanity Fair.
A recent series of personal issues has made navigating her already complex life more difficult, close associates said. In the last five years, Ms. Leibovitz lost her father, her mother and her companion, Susan Sontag; added two children to her family and oversaw the costly and controversial renovation of three properties in Greenwich Village.
Charlie Scheips, the former director of the Cond Nast photo archive who helped Ms. Leibovitz make a deal last year with an auction house to sell prints of her photographs, said that when he spoke to her recently, he was told: "I'm really under the gun. I've got three daughters, I lost my spouse. I've got too many jobs to do and it's chaos."
Matthew Hiltzik, a spokesman for Ms. Leibovitz, pointed a finger at the lender suing Ms. Leibovitz, Art Capital Group, a company in New York with a history of litigation over its boutique loans to artists, art dealers and collectors, who pledge their art works as collateral. "Annie is in the same shoes as many other people involved with Art Capital," Mr. Hiltzik said.