normal Minecarts and Powered rails aren't working.

When i will make rails I will place a normal minecart (not a hopper or furnace one) the minecart will shake like you are breaking it. This is only when you are going along a straight stretch. It doesn't happen when going downhill. With the powered rails they do not work and propel any minecarts forward (including hopper furnace ect.). This happens in all gamemodes.