The same thing is happening to me today. I thought I was losing my marbles. Mine was with trees. Spent 30 energy to chop a tree, the energy was subtracted, the "worker" started chopping, then poof! Gone! No chopped wood, no worker, required chops still showing "30", and the only thing that's changed is the energy. I couldn't believe my eyes! What did I do? I repeated the process on the very same tree: 30 energy subtracted, no worker, no chopped wood, and required chops still show 30. I think this might be a relatively important issue for EA to look into. How do you continue to play the game if you can't clear the land? I'm out 60 energy with nothing to show for it.