A larger-than-expected rise in weekly jobless claims and a fifth consecutive monthly decline in import prices have U.S. stocks lower this morning, potentially headed for a fourth straight day in the red. Among the equities in focus are networking concern Ciena Corporation (NYSE:CIEN), retail giant Wal-Mart Stores, Inc. (NYSE:WMT), and restaurant interest Yum! Brands, Inc. (NYSE:YUM).