Kurt Siemon, Plaintiff-appellant, v. At&t Corporation, Formerly Known As American Telephone Andtelegraph Company, a New York Corporation; At&t Globalbusiness Communications Systems, a Division of At&tcorporation; At&t Sickness and Accident Disability Benefitplan, Defendants--appellees, 113 F.3d 1175 (10th Cir. 1997)