Enchants not working

I was playing four pillar survival when I enchanted my diamond sword I got Fire Aspect I and I was so happy. (This was in 1.6.2) Then I went to snapshot 13w38c and I hit a creeper with my sword and nothing happened. I was really confused so I thought maybe it got changed to where its only some of the time then I hit a skeleton and nothing happened. Then I was super worried I thought I was lagging I pressed F3 I had 30 FPS. After that I came here.