Norton Healthcare and Anthem insurance officials returned to the negotiating table Wednesday, saying afterward that eight hours of talks aimed at ending a contract dispute were productive.The two companies have been at odds for months. Norton left the Anthem network July 1, citing problems with claims processing and other issues. Anthem says Norton wants to raise its rates to unreasonably high levels.The dispute has left Anthem customers paying out-of-network rates for Norton services.The talks are scheduled to resume Friday.