At LGA, we start accelerating at full thrust. Must have been about 80-90 kts when all of the sudden, the engines go right to idle. But no brakes. We just coast all the way down to the far end of the runway, turn on to the taxiway and head back to where we came from.

We pax were all scratching our heads trying to figure out what happened, until the pilot finally comes on with an explaination. It turns out that after we had started our roll, ATC had urgently come on the radio and said something to the effect of "Oh, we're sorry, when we gave you clearance to take off, we really didn't mean it. Could you please pull off the runway and go to the rear of the (45-minutes-before-you-get-to-takeoff-again) line?" Ugh and duh.