Is a computer implicated in the D.C. train crash that killed nine?

Sarah Karush and Brian Westley, writers for the Associated Press, report that a Computer failure may have caused D.C. train crash.

Investigators looking into the deadly crash of two Metro transit trains focused Tuesday on why a computerized system failed to halt an oncoming train, and why the train failed to stop even though the emergency brake was pressed.

This isn't the first time that Metro's automated system has been called into question.
In June 2005, Metro experienced a close call because of signal troubles in a tunnel under the Potomac River. A train operator noticed he was getting too close to the train ahead of him even though the system indicated the track was clear. He hit the emergency brake in time, as did the operator of another train behind him.