The U.S. Supreme Court reconvenes Oct. 4 with a new justice: Roth Bader Ginsburg. President Clinton's choice for the seat vacated by Justice Byron R. White joins a conservative court that has been assuming a lower profile on controversial issues. Some conservatives fear Ginsburg will breathe new life into liberal judicial activism. Many liberals, however, say Ginsburg is too cautious in using judicial power to bring about social change. As the court begins its work, some cases involving familiar issues already are on the docket, including racial redistricting and abortion clinic violence. But other heated disputes, such as affirmative action and homosexual rights, are not. Ginsburg's actions will be watched closely for clues about how she will affect the balance of power on the nation's highest court.