when a player (creative, survival or adventure) gets hit by a tnt blast on a map runnig on a server (local or distant, I tested both) the player will start to move, then will be teleported back and the server console gives a "player moved too fast" error. Tested with flight enabled or not, as well as with op or not.
Easy to reproduce, just stack two or three tnt and light them up, stand close to ground zero, and wait for the blast.

Very troublesome on one of my maps, since it uses tnt fast travel for non op players (command that gives resistance to player plus spawns a heckload of tnt going at the same tick at him)

I did try to search, but did not find any relation between explosions and the moved too fast error, sorry if this has already been reported.