SAN FRANCISCO (MarketWatch) - Calpine Corp. stock closed down more than 9% on Friday after the independent power producer posted its third-quarter results, which it subsequently had to correct, and Fitch Ratings cut the firm's credit rating. San Jose, Calif.-based Calpine turned in a third-quarter loss on Thursday that was wider than analysts expected. See full story. The company then later Thursday corrected its press release detailing its financial results to account for certain charges and items. Among the changes, Calpine corrected its earnings before income taxes depreciation and amortization for the nine-month-period through Sept. 30 to $880.4 million, down...