JPMorgan Chase ( JPM) reported a 68% gain in profits, fueled by the solid performance of its investment bank. But the retail banking operation of the nation's third-largest lender showed some weakness in the fourth quarter, which could be an indication of potential trouble ahead for JPMorgan and other banks. It's one reason shares of JPMorgan Chase were flat in afternoon trading, even though earnings and revenue surpassed analyst expectations. The stock most recently traded at $48.38. There's no denying that much of the headline news coming from JPMorgan was positive. In the quarter, JPMorgan earned $4.53 billion, or $1.26 a share, compared to $2.7 billion, or 76 cents, a year ago. On an operating basis, which excludes a big gain on the sale of the bank's corporate trust business, JPMorgan earned $3.9 billion, or $1.09 a share. Total revenue rose 14% to $16.9 billion. The quarter benefited from a big 51% surge in profit at JPMorgan's investment bank. Fees from traditional investment banking work and revenue generated from proprietary trading generated $1 billion in profit for the group. The bank's private equity business also had solid results. Revenue rose 33% from the third quarter to $250 million. But it was another story at JPMorgan's retail bank. Profit made by its 3,079 bank branches fell by 7.5%, to $619 million. Revenue squeaked higher by just 4%, to $2.9 billion. Noninterest expenses from regional banking, meanwhile, rose 6%, to $1.73 billion.