There was profit-booking in FMCG, auto, realty, banks, capital goods and consumer durable sector stocks that made the 30-share index fall.
Earlier, the Sensex traded positive and the Nifty once again breached the 7,900-level on sentiments bolstered by higher global cues and sustained FII buying.
The 30-share Sensex opened higher at 26,496.29 and fluctuated to a high of 26,504.52 and a low of 26,336.25 before quoting 26,405.41 points at 1100 hours.
It showed a loss of 76.49 points, or 0.29 per cent, to 26,344.18.
The NSE 50-share barometer Nifty also marked new peak of 7,922.70. It was down by 23.35 points, or 0.30 per cent, to 7,874.15 at 1100 hours.
Major losers were ONGC (1.82 per cent), HeroMoto (0.74 per cent), SBIN (1.08 per cent), ITC (0.60 per cent), Hind Unilever (0.89 per cent), Axis Bank (1.04 per cent) and L&T (0.77 per cent).
Most Asian stocks were trading higher after strong US housing data lifted American stocks.
Key benchmark indices in Taiwan, Singapore, Hong Kong and Indonesia rose 0.11-0.43 per cent, while major indices in China, Japan and South Korea fell 0.02-0.14 per cent.
Meanwhile, Foreign Portfolio Investors (FPIs) bought shares worth a net Rs 559.39 crore yesterday, as per provisional data from the stock exchanges.