CNBC’s Mary Thompson on US markets - On Wall Street, the Dow’s triple digit rally faded as stocks closed lower. The Federal Reserve’s decision to cut a key interest rate by 0.5% was as expected.

The blue-chip average fell 37 points to 12,442, the S&P dropped 6.5 points and the Nasdaq closed down 9 points. Financial stocks faced a decline today. Among the biggest losers were Dupont Insurance. MBIA and Ambac posted double-digit percentage declines as big short-sellers stepped up huge campaign against the companies, saying losses in their subprime related holdings are much bigger than estimated. Also pressuring their shares were fears that they were going to lose their AAA credit ratings.

Among the Dow stocks, Merck declined more than 2.5% as Q4 sales of the drug company’s cervical cancer vaccine proved disappointing, while Boeing closed higher after the aviation giant raised its profit outlook for 2008.