NASDAQ Cancelling Trades After Crazy Day in The Market

Trying to figure out what to think about this: (from BusinessWeek)
The Nasdaq said after markets closed that it will cancel all trades of stocks that moved more than 60 percent from their price at, or immediately prior to, 2:40 p.m., when the slide started. The cancellation applies to trades executed between 2:40 p.m. and 3 p.m.
Were there true “errors” leading to these trades (e.g. running trades that weren’t placed, or trades triggered because a stocks price was listed incorrectly)? Or were there just a bunch of people with stop losses …