Upon placing a block or destroying one, there will be a huge lag spike about 5-50% of the time (depending on how fast the game is running otherwise: 60-70fps = 5%, 10-15fps = 50%) that will result in 2-3 blocks being placed or destroyed with even the briefest of clicks instead of the intended one. This makes the game virtually unplayable because the placement and destruction of blocks becomes essentially out of the player's control. I have done personal testing to confirm that it is not a hardware glitch; both my and others' experiences have been that the problem occurs only in Minecraft (not in any other application) and persists whilst using the trackpad instead as well as after replacing the mouse with a new one. This bug will still occur with no other applications open and no other users logged in. It sometimes takes a little while to materialize, and sometimes will not materialize at all; however, it is reproducible and persistent, striking perhaps every other to every third time I play and often setting in within fifteen minutes of beginning play. Getting the game to lag to about 10-20fps can help the issue become far more readily apparent, although I have seen it occur at frame-rates as high as 73fps.