Using the snapshot there is a lot of server-side lag. This lag is present on singleplayer, and on multiplayer, to other players as well. TNT doesn't blow up on time, redstone clocks are very slow, beacon effects disappear and reappear, etc. Framerate seems unaffected.
I have witnessed multiple instance of player movement being affected. I walked forward and was "teleported" back to my previous position.
There are already a number of bugs relating to lag and FPS drops in the newest snapshots, I would suggest you look through those to see if any of the suggested workarounds work, or if your issue duplicates one of them. You can attach a crash report here (F3 + C for 10 seconds, stored in /minecraft/crash-reports/crash-<DATE>-client.txt). You also need to update your Java to the 1.7.0_51 version.