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I just downloaded the joint US-Canada report and skimmed though it - VERY detailed ... here's an excerpt, the summary, from section 4:

4. How and Why the Blackout Began

Summary

This chapter explains the major events?electrical,
computer, and human?that occurred as the
blackout evolved on August 14, 2003, and identifies
the causes of the initiation of the blackout. It
also lists initial findings concerning violations of
NERC reliability standards. It presents facts collected
by the investigation team and does not offer
speculative or unconfirmed information or
hypotheses. Some of the information presented
here, such as the timing of specific electrical
events, updates the Sequence of Events1 released
earlier by the Task Force.

The period covered in this chapter begins at 12:15
Eastern Daylight Time (EDT) on August 14, 2003
when inaccurate input data rendered MISO?s state
estimator (a system monitoring tool) ineffective.
At 13:31 EDT, FE?s Eastlake 5 generation unit tripped
and shut down automatically. Shortly after
14:14 EDT, the alarm and logging system in FE?s
control room failed and was not restored until
after the blackout. After 15:05 EDT, some of FE?s
345-kV transmission lines began tripping out
because the lines were contacting overgrown trees
within the lines? right-of-way areas.

By around 15:46 EDT when FE, MISO and neighboring
utilities had begun to realize that the FE
system was in jeopardy, the only way that the
blackout might have been averted would have
been to drop at least 1,500 to 2,500 MW of load
around Cleveland and Akron, and at this time the
amount of load reduction required was increasing
rapidly. No such effort wasmade, however, and by
15:46 EDT it may already have been too late
regardless of any such effort. After 15:46 EDT, the
loss of some of FE?s key 345-kV lines in northern
Ohio caused its underlying network of 138-kV
lines to begin to fail, leading in turn to the loss of
FE?s Sammis-Star 345-kV line at 16:06 EDT. The
chapter concludes with the loss of FE?s Sammis-
Star line, the event that triggered the uncontrollable
cascade portion of the blackout sequence.

The loss of the Sammis-Star line triggered the cascade
because it shut down the 345-kV path into
northern Ohio from eastern Ohio. Although the
area around Akron, Ohio was already blacked out
due to earlier events, most of northern Ohio
remained interconnected and electricity demand
was high. This meant that the loss of the heavily
overloaded Sammis-Star line instantly created
major and unsustainable burdens on lines in adjacent
areas, and the cascade spread rapidly as lines
and generating units automatically took themselves
out of service to avoid physical damage.

Chapter Organization

This chapter is divided into several phases that
correlate to major changes within the FirstEnergy
system and the surrounding area in the hours
leading up to the cascade:

- Phase 1: A normal afternoon degrades
- Phase 2: FE?s computer failures
- Phase 3: Three FE 345-kV transmission line failures
and many phone calls
- Phase 4: The collapse of the FE 138-kV system
and the loss of the Sammis-Star line

Key events within each phase are summarized in
Figure 4.1, a timeline of major events in the origin
of the blackout in Ohio. The discussion that follows
highlights and explains these significant
events within each phase and explains how the
events were related to one another and to the
cascade.