I finished a roll of film in my OM2 this afternoon and loaded a new one. After loading I wound on from the start mark to check that it was winding on correctly and then closed the back. The shutter fired as it should. But after I wound on to the second mark, the shutter release and the wind on lever seem to be locked. The mirror is not locked up and the check/reset indicate that the batteries are not low. Does anyone know what to do about this? Regards. Chris B.