pmuolo@imfpubs.com Fannie Mae posted a net profit of $1.3 billion in the fourth quarter, a 66 percent decline sequentially, blaming the earnings downdraft on a reduction in the fair value of its derivatives. The GSE “derivative problem” also plagued the fourth quarter results of Freddie Mac, which reported a slim profit of $227 million after writing down its derivatives by $3.4 billion. …