Minecraft 1.7 problems?

Ever since the 1.7 update I have not been able to save my world properly. I'll build something, then hit save and quit and when I log back in everything I have built is gone! My resources that I used are gone but so is what I built with them. What should I do? It might be unrelated to the 1.7 update. All I know is that this started yesterday. Please help!