The Sensex at the Bombay Stock Exchange failed to maintain the 30,000-level in late morning trade today. After rising 134 points in opening trade, the 30-share index erased its gains and was trading 55 points down at 29,864, when reports last came in.The Nifty at the National Stock Exchange was trading 16 points down at 9,288. At the foreign exchange market, the rupee rebounded by 24 paise to 64 rupees against the US dollar in opening trade today.