Ernest Lorch, who once headed a Midtown leveraged-buyout firm, stepped down as director of the Riverside Church youth basketball program in 2002 because the Manhattan district attorney's office is investigating his relationship with the former player, Robert Holmes, officials at the interdenominational church said yesterday. Mr. Lorch, the coach of the program's team, the Riverside Hawks, gave up the directorship pending the resolution of the investigation, the church said in a statement. Mr. Lorch is a lawyer and the former chief executive of Dyson-Kissner-Moran, a leveraged-buyout firm on Fifth Avenue. He has been a powerful figure in New York City amateur basketball since taking over the program at Riverside in 1961.