Rollercoaster

When the markets opened today, all the indexes shot through the roof and it looked like it was going to be a positive day. With oil down 5% on the day after Gustav slowed down, it looked like a typical reaction by the equities. But at the end of the day, the Dow, S&P, and Nasdaq all ended in negative territory, while oil prices remained at 5-month lows. Huh?