How to reproduce:
1. Make a redstone line a least 64 blocks long (with repeaters) and tnt at the end
2. Power redstone wire

Expected result: crater at end of the line
Actual Result: Dropped items and some redstone destroyed, but no crater. The when blocks are updated they disappear.

Video: http://www.youtube.com/watch?v=wbZ7FEe-oq0&feature=youtu.be
World download is attached.