U.S. stocks started the fourth quarter on a positive note, with the Dow (INDEX: ^DJI) gaining 0.6%, while the broader S&P 500 (INDEX: ^GSPC) rose 0.3%, but both indexes closed well off their highs of the session. Perhaps investors weren't all that impressed by Ben Bernanke's spirited defense of the Federal Reserve's policies in a speech at the Economic Club of Indiana this afternoon. The most significant aspect of the speech was the chairman's emphasis that the Fed will keep rates low even once the economic recovery gains pace. Bernanke (rightly) denied that the central bank was at risk of creating runaway inflation, but he said nothing about runaway stock/risk asset prices.

In stock-specific news, JPMorgan Chase's (NYSE: JPM) shares were ambushed in after-hours trading -- down 1% after a 1.2% gain in the regular session -- by news that the New York Attorney General is bringing suit against the bank relating to the sale of mortgage-backed securities by Bear Stearns in 2006 and 2007 (JPMorgan acquired Bear Stearns in 2008). The lawsuit alleges investors lost $22.5 billion on more than a hundred such securities -- a quarter of their original value.

Did Bear Stearns mis-sell the securities? Almost certainly -- whether intentionally or otherwise. Should investors who bought the securities have known better? Given where home prices were by 2006, definitely. Peak-to-trough from June 2006 through March 2011, the Shiller-Case national home price index fell by a third; by that measure, the investors who bought the mortgage bonds in question from Bear fared better than expected. Either way, using $22.5 billion as a basis for calculating potential damages, you're going to come up with a big number. That's not good news for JPMorgan -- expect the shares to continue to come under pressure tomorrow. That the housing/ credit bubble should come back to haunt JPMorgan at this stage illustrates why The Motley Fool's top banking analyst believes The Only Big Bank Built to Lastis another institution; to find out which bank deserves that title, request our free report today.