Recently, I needed to change the session save_path in my program under Windows. With an ini_set('session.save_path', '../data/sessions'); (and session.gc_divisor = 1 for test), I always obtain 'Error #8 session_start(): ps_files_cleanup_dir: opendir(../data/sessions) failed: Result too large'.
I corrected this by changing with ini_set('session.save_path', realpath('../data/sessions'));