Erasing all its initial gains, the Sensex at the Bombay Stock Exchange was down 36 points, or 0.2 percent, at 17,238 in afternoon trade, a short while ago. Earlier in the morning, however, the Sensex had gained 73 points, or 0.4 per cent, to 17,346 on fresh buying by funds and retail investors at attractive lower levels. The 30-share Sensex has already lost more than 645 points in the past three trading sessions. Other regional markets in China, Hong Kong, Indonesia, South Korea and Taiwan were down by between 0.2 percent and 0.8 percent, as investors booked profits after recent gains