This has been around for a long while. Play on any Parkour server or other movement based games and it really becomes a problem. I can get it to happen almost every time when I am in creative mode. You start sprinting, stop sprinting, then quickly pick up sprinting again with very little time not sprinting in between. Reproduced in 1.5.2.
This doesn't happen for me, even at 30 mil blocks.
That's one strange bug, which I guess is to be expected for the new rendering optimisations.
14w20b - Windows 7 - Java 7