A RealNetworks spokesman said the company was considering a monthly fee of about $10, among other pricing possibilities, while an AOL spokeswoman declined to speculate.

"Our policy is to cooperate when presented with a formal request," said Wendy Goldberg, an AOL spokeswoman.

An AOL spokeswoman said the lawsuit "is without merit and has no basis in fact or in law."

But Kathy McKiernan, an AOL spokeswoman, said that the company was experiencing its fastest growth and lowest turnover rate ever.

"It affects people in different ways," said Ann Brackbill, an AOL spokeswoman.

"A certain status has developed" around the low numbers, said Cindy Harvey, an AOL spokeswoman.

"We are convinced we will successfully address the issues raised in our review," said Kathy McKiernan, an AOL spokeswoman.

"We are absolutely sincere" about achieving interoperability, said Tricia Primrose, an AOL spokeswoman.

An AOL spokeswoman said the company had no further comment.

(The Macintosh version will lag by a few weeks, an AOL spokeswoman said.)