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NEW YORK, July 21 (Reuters) - Comerica Inc (CMA.N: Quote, Profile, Research), a large U.S. regional bank, posted its second straight quarterly loss, hurt by credit problems tied to residential real estate developers.

"The key credit issue for us remains in our commercial real estate line of business, predominantly residential real estate development," Chief Executive Ralph Babb said in a statement.

He said "the prolonged recession has recently taken a toll on our residential real estate development portfolio" in Florida. But California has shown signs of stabilization.

Comerica's net loss attributable to common shareholders was $16 million, or 10 cents per share, compared with a year-earlier profit of $56 million, or 37 cents, the Dallas-based bank said on Tuesday. Before preferred stock dividends, net income totaled $18 million for the quarter.

Analysts, on average, looked for a loss of 44 cents per share, according to Reuters Estimates.