Clean's link is the first theory that seems in any way plausible to explain this mystery.
I was leaning toward the pilot somehow going loco and hijacking the plane, but since it appears pretty sure the plane flew 8 hours until it ran out of fuel and crashed in the ocean, that theory has a lot of holes. Why would he do it, and why wouldn't the other airline personnel and/or the passengers do something to thwart the plan?
The electrical fire scenario is much more logical. Everyone was dead, and the plane continued to fly until it ran out of fuel and crashed.
We may never know what really happened, though.