This could get interesting. Stay tuned...

From this AP report:

Several hours after the power went out, Jim Munson, a spokesman for Canadian Prime Minister Jean Chretien said: "We have been informed that lightning struck a power plant in the Niagara region on the U.S. side." The premier's office later said a fire at the Niagara plant in New York caused the blackout, while the defense minister said the fire was at a Pennsylvania nuclear plant.

"That is absolutely not true," said Pennsylvania Emergency Management Agency spokeswoman Maria Smith. "It's bizarre. We have a direct line to each of our five (nuclear) power plants and they are all running at 100 percent ...

There's not even a trash can fire, we would know." Brian Warner of the New York Power Authority said he wasn't sure where the power failure originated. "The New York Power Authority's Niagara Power Project has at no time during this incident cease to operate. We also have not experienced a lightning strike at that facility," he said.

U.S. officials were looking at a power transmission problem from Canada as the most likely cause of the biggest outage in U.S. history, said a spokeswoman for New York Gov. George Pataki. There was no sign of terrorism, officials in New York and Washington agreed.