Minecraft block break lag?

I'm playing vanilla single player. When I try to break a block, it breaks, comes back, and stays for up to 15 seconds before breaking for good, as well as dropping whatever it drops. This is a new world, and a survival level I made a while back works just fine. This has happened to me before with new world's, but is seems like they usually work eventually. And yes, I have gotten out of Minecraft and back into it. It hasn't helped.