The Eugene O’Neill Theater Center’s shift to having a single artistic director oversee all of its programs was a factor in the sudden departure last year of James Houghton, the head of the prestigious O’Neill Playwrights Conference. Following the abrupt resignation last summer of J Ranelli, the center’s first overall artistic director, the O’Neill is now looking not for someone to fill that spot but simply for an artistic director for the playwrights conference. (Second item.)