Trading on the London Stock Exchange has been halted for most of today due to a "connectivity issue" that has left UK traders unable to respond to a surge in U.S. equities in the wake of the government's weekend rescue of the Fannie Mae and Freddie Mac mortgage agencies.
The London Times describes what's known of the problem:
The LSE suspended connection to the exchange before 9am today after some customers experienced problems. The operator admitted it was unsure when trading will restart today, while the cause of the problem is not yet known. One City insider said that traders will lose "millions and millions and millions" of commission on deals, adding that today's closedown is "very serious and disastrous." It appears there is a fault with the SETS electronic trading platform since the Johannesburg Stock Exchange also suspended trading.