The best thing we can say about Thursday's stock market trading is that it is now over. The Dow fell 317 points, erasing all of its gains for the year. The S&P 500 and Nasdaq fell sharply as well, each down about 2%. They gave back the all the gains they had made in July. Heavy selling overseas, driven by worries about Argentina's latest debt default and more problems with a big Portuguese bank, combined with a slew of negative earnings and a disappointing outlook on manufacturing from the Federal Reserve Bank of Chicago to drop stocks. The VIX (VIX), a gauge of market volatility, jumped almost 27%. CNNMoney's Fear ... (full story)