Sensex traded slightly lower after opening on a flat note on Thursday.At 10.14 a.m., the Sensex was trading 55.45 points lower at 39,160.19. It opened at 39,204.47 from its Wednesday's close 39,215.64.The Nifty was trading 20.10 points lower at 11,667.40.Yes Bank was the top loser, down over 10 per cent on the BSE after poor quarterly numbers announced on Thursday.Care Rating was down over 4 per cent after the company decided to place Rajesh Mokashi, Managing Director & CEO of CARE, on leave, with immediate effect.This is the second rating agency head after ICRA's Naresh Thakkar to be send on "leave" after an anonymous complaint to SEBI, the market regulator alleged that there were lapses in ratings.Several rating agencies had given high rating to IL&FS when the ground reality of the company was far from being in good shape.