this is a glitch with the snapshot i accidentally played on my favorite world in the snapshot and when i went back to 1.7.4 all inventorys of all blocks that can hold items and all player inventorys are empty. my solution is just to fill them back up with what i had before so its no big deal but im giving you a heads up so you guys can hopefully fix it before 1.8 comes out.the same thing happened to my friend on his world but it was on a mac so i dont think this is related to the operating system.