Jim Balsillie, the co-chief executive of BlackBerry maker Research In Motion Ltd., has stepped down as chairman as the company announced a $250-million earnings restatement relating to mistakes in how it granted stock options in the past.

RIM said it found no intentional misconduct by executives, directors or other employees responsible for administering options grants. However, the restatement, which affects the period from 2004 to the first quarter of 2007, is much larger than the company initially estimated.