For a performer, winning an Oscar can be both a blessing and a curse. The Academy Award sometimes can lead to bigger and better roles, or it can lead to a stagnation as the actor tries to live up to unrealistic expectations. When Marisa Tomei's name was called out as the recipient of the Best Supporting Actress statue at the 1993 Oscar telecast, some unkind people began unfounded and nasty rumors that she was given the award erroneously, particularly as her competition included such stalwart veterans as Judy Davis, Joan Plowright, Vanessa Redgrave and Miranda Richardson. What those wags failed