The parent company of Toledo Edison did not accept full responsibility for the Aug. 14 blackout affecting 50 million customers in eight Midwestern and Northeastern states and portions of Canada.

But the firm's report this week attributes the failure of its warning system to a software malfunction triggered when two problems on the grid dumped data into the computer at the same millisecond.

FirstEnergy called the software failure "a highly unusual and unforeseeable event," but said the vendor has patched the flaw pending installation of a $10 million replacement computer system by June 1.

Northern Ohio's major electric utility filed its report Monday in response to a Public Utilities Commission of Ohio order that it detail how it will address issues targeted last November in a blackout post-mortem conducted by an international task force. The task force determined that the blackout began in Ohio when three FirstEnergy high-voltage lines were short-circuited by trees. The company's alarm system failed to warn control-room operators who, in turn, did not take corresponding corrective measures to prevent the spread of the problem from Ohio to Michigan and beyond.

The November PUCO order demanded a corrective action plan from FirstEnergy even as the regulatory agency conceded the Akron-based company disagreed with the conclusion that the blackout was its fault.

The company continues to maintain that those cited events by the task force did not alone cause the blackout.

The investigation as well as the continuing shutdown of the Davis- Besse nuclear power plant occur as the PUCO is considering a company request to extend its current rates, set to expire Dec. 31, 2005, for three more years.

Agency spokesman Shana Gerber said the commission will study FirstEnergy's response and decide whether additional action is necessary.

The utility noted it had entered into a contract to replace its energy management computer system at its control centers in Akron and Reading, Pa., before the blackout occurred. The replacement is expected to include a number of redundancies to serve as emergency backups.

Ohio Deputy Consumers' Counsel Eric Stephens took issue with FirstEnergy's characterization of itself in the report as "an industry leader in the deployment of information technology."

"If being a leader is being singled out for the largest blackout in history, then I don't want to be a leader," he said. "That's just a nice way to put a spin on a difficult situation for the company."

Mr. Stephens criticized the company for not accepting responsibility for the blackout and noted that neither the regulatory order nor FirstEnergy's response addresses tree- trimming.

In the report, the company said it:

--Will install large-screen projection systems in its control centers so operating staff can monitor system conditions.

--Will fully implement a more formalized staff training program, including computer simulations.

--Has hired additional trainers and identified a training leader.