The "confirm flight computer is not in start-up" call is part of the vehicle safing process after an abort or hold is called. It is heard immediately after any hold or abort during the terminal count. This does not indicate the cause of the abort.

True... thank you for the correction. I think the most precise real cause indicated was "abnormal data from stage 1" which doesn't mean much.

Elon Musk just clarified what happened: "Saw pressure fluctuations on Falcon boost stage liquid oxygen tank. Want to be super careful, so pushing launch to Thurs."

https://twitter.com/elonmusk/status/405134552458620928

I was watching the stream. Immediately prior to the final hold (more accurately "Hold! Hold, Hold, Hold!") there was a clearly abnormal burst of fuel vented from the midpoint of the vehicle, in two or three bursts. Happened several seconds after they pulled back the support structure. My eyes widened at that point. "Is this normal?!" I thought, and was glad to hear the hold command!

When can we confirm that they missed their window?

(Edit: new window is Thanksgiving day, one minute later than today. Might have to stream this one to the Apple TV for the whole family…)

Just confirmed on webcast but even before the launch window only extended to 6:43 EST, not enough time to reset the countdown.

It's been called off. Next launch window in three days, one minute later than today's window.

Entertainment during Thanksgiving dinner. :-)

Just confirmed. It'll launch on Thursday instead.

They just did on the livestream.

argh, so nerve-wracking