In 13w25b, I was in a creative world and randomly tried to break a block with an iron sword and was not able to destroy it. I later tried the wooden, stone, gold, diamond swords and none of them were able to break any block. While I could break any block using my hands or any other item. I also tested in survival mode if I could destroy blocks with all of these swords and it worked. So the problem is only in creative mode. Also I am sorry that I don't know if this bug exists in any previous versions.