The Bombay Stock Exchange Sensex erased early gains in the mid-session today to trade lower by over 45.30 points on profit selling in heavy-weight stocks in the metal sector. The Sensex, which opened nearly 75 points higher, fell back to record a loss top trade at 17060.80 at 1340 hrs with metal companies falling as commodity prices declined. The fall was capped after shares of software exporting firms edged up on dollar firming against the rupee, raising hopes of an improvement in revenues of information technology companies.The wide-based National Stock Exchange index Nifty fell by 20.20 points to 5088.70 at the same time. It had touched the day's high of 5,131.30 points.