Manhattan Assemblyman Adam Clayton Powell 4th is being investigated on a rape accusation for the second time in as many months, law enforcement sources said yesterday. A woman told police that after meeting Powell at a party Thursday night, they went to her West Side apartment, where he raped her at about 8:30 p.m., police officials said. After he left, she called 911. She was examined at St. Luke's Hospital, sources said. A high-ranking law enforcement source described the woman as "an acquaintance" of Powell's, but not a co-worker or employee. Police sources said Powell, 42, has been questioned but...