Sybille Bammer, as I suspected, has withdrawn from Charleston; I'm sure it must be because of her back. Also withdrawing are Caroline Wozniacki, Meilen Tu (a fixture at the Cup), Nuria Llagostera Vives (another fixture), and Peng Shuai (also a regular player there).
Replacing them, respectively, are: Alicia Molik, Yuliana Fedak, Ekaterina Bychkova, Julie Ditty, and Anastasia Rodionova. Yuan Meng replaces Venus Williams, and the talented Sorana Cirstea replaces Justine Henin.
I am especially disappointed to learn that Wozniacki has withdrawn; I really wanted to see her play.