Riverstone Networks ( RSTN) will break even at best in the fourth quarter and said it will cut an unspecified number of jobs as it contends with the extended downturn in the telecommunications market. The company's stock was selling off in the premarket session, down $1.59, or 21%, to $6 on Instinet. The Santa Clara, Calif., network equipment firm expects to break even or report a loss before items for the fourth quarter on revenue of $50 million to $54 million. Analysts surveyed by Thomson Financial/First Call had expected the company to earn 4 cents a share in the period. Riverstone will cut out about 10% of its costs through measures including job cuts and take fourth-quarter charges between $26 million and $30 million, it said.