This is usually caused by lag. You can wait out the problem, it does not last long, but if you are really bugged by it you can defrag your computer of gat software that will speed it up.
right click
As of right now, being the current version of 1.7.3, that problem does not exist unless you are running a version of Minecraft that is unstable.
Right click.
right click it.
You right click
Right Click
Hold Right Click.
You put your mouse on it and right click. And right click again to put stuff in it.Kayla
you right click on a block
right click + hold
right click a pig
Right-click the railcart (or minecart) to get in (or out).