Three Twin Cities nurses who crossed their union's picket line during a mass walkout June 10 say they were harassed by the union after the fact through letters calling them to a disciplinary hearing. The nurses, all from Children's Hospitals and Clinics of Minnesota, say they resigned from the union before the 24-hour walkout in order to work behind the picket lines. Nonetheless, they received letters from the Minnesota Nurses Association saying they may be subject to reprimand, censure or expulsion. The nurses filed a complaint against the MNA late Wednesday with the National Labor Relations Board. In the past, it's been the MNA that's filed a flurry of federal complaints against the nurses' employers.