Minecraft wierd lag?/ no update of blocks?

In the pre-release version is I was testing around some Redstone mechanics and then this whole delay started. It was about seven times slower for blocks to update like Redstone. I could place blocks fine but Redstone would'int update. This happened in Minecraft 1.8, pre-release 2, and pre-release 3. Those were the tested versions. Please help because this is really annoying to deal with. Pressure plate stay down Redstone Blocks won't update Redstone, repeaters delay is a lot longer. I am trying to create a awesome invention, but this is slowing me down, please I need your help