By the end of 2010, about half of all commercial real estate mortgages will be underwater, said Elizabeth Warren, chairperson of the TARP Congressional Oversight Panel, in a wide-ranging interview on Monday. “They are [mostly] concentrated in the mid-sized banks,” Warren said. “We now have 2,988 banks—mostly midsized, that have these dangerous concentrations in commercial real estate lending.” As a result, the economy will face another “very serious problem” that will have to be resolved over the next three years, she said, adding that things are unlikely to return to normalcy in 2010.