I've had this same issue as of Snapshot 13w24b. Fix: (Worked for Me): Open the world to lan and for other players settings, turn cheats on and I broke the block and it worked, I don't know how this is possible, but the block does not reappear and now breaks normally and drops the block normally. I was thinking maybe lag from the singleplayer server? I'm not completely sure but it worked. EDIT: After turning on your lan world and activating cheats, you may have to Save and Quit to Title and go back to your singleplayer world.
Collin R Sawyer
I've had this same issue as of Snapshot 13w24b.
Fix: (Worked for Me):
Open the world to lan and for other players settings, turn cheats on and I broke the block and it worked, I don't know how this is possible, but the block does not reappear and now breaks normally and drops the block normally. I was thinking maybe lag from the singleplayer server? I'm not completely sure but it worked.
EDIT:
After turning on your lan world and activating cheats, you may have to Save and Quit to Title and go back to your singleplayer world.