I had a rejected take off about 2 years ago from Calgary to LHR flight. BA dreamliner, trundling down the taxiway turns on to runway, power on and then power off and more trundling and stopped.
we sat for a couple of minutes then pilot came on and aplogised for rejecting take off because of instrument indicator problems (I think) which was the first I was aware of a problem. We were parked just off the runway while they sorted it out. After a few minutes whatever was the problem was fixed and we trundled back and took off.
The worrying thing was I could hear the stewardess behind us (I was in last row) and she was extremely worried asking her colleagues for reassurance. Got back safe so non event?