The New York Stock Exchange suspended trading in 216 companies Monday as a server upgrade hit order delivery in the effected stocks.
The bungled upgrade scrambled the Exchange's order matching engines, leading to a day of confusion for traders who received contradictory alerts about the status of their orders.
The problems kicked off at the start of trading after Nyse moved the stock symbols to new servers as part of a phased migration to a new universal trading platform.
Trading in the stocks continued on other exchanges as Nyse investigated the problems. By day's end the Exchange told traders that all open orders in the stocks had been cancelled. A list of consolidated closing prices based on trading elsewhere was distributed by Nyse via e-mail and on its Web site.
The problem is the latest in a series of mishaps to have hit US exchanges since the May 2008 flash crash, which highlighted the complexities of trading in global electronic markets.
Nyse says that it expects trading to resume normally Tuesday.