Entity lag

I have some issues with entities.
All of them (including minecarts or boats) have some sort of lag. For example, when they moves, they goes a lot slower of the normal; even when i punch any type of monster.
To make sure that it wasn't my computer, i test it out on minecraft 1.7.9, but it didn't happen.
Thank you for attention.
P.S:
There is no way to reproduce the problem.