Abrupt market correction
There were a couple of issues that haven't helped calm things down. First, the NYSE's systems somehow got behind on trades and switched to a back-up server, which led to a radical one minute drop in the afternoon. Traders, at least ones not on the floor of an exchange, were in a sense flying blind for an hour or so. Second, bond mutual funds strangely took on average an hour longer than usual to report their results for the day. This is a different issue and had no trading effect, but one can't help but wonder why---just the volume or something else?
This could be an ultimately healthy market event but it's unlikely to feel that way in the morning. Volatility is back and regardless of the near term trading action, this stings in a way that will linger. That said, it is still certain that buyers are lurking, and will likely attempt to lead a rally soon.